So long as any first coats of epoxy are cured and any bloom is cleaned, I can't see how properly prepared epoxy of a different quality brand would fail in any way.  If the thermal expansion coefficients or shear strengths are dramatically different, you might have issues, but only in highly loaded cases or extreme temperature changes.  That said, if you go to the Mas and West sites, you can probably find data sheets showing the cured properties of their more common epoxies and compare them.  

The only thing I can think of is that the West system uses (or used) a lot of 4:1 mixes rather than the 2:1 of Mas.  I found the hard way that with 4:1 or higher, you need to be more precise in your measurements.  I've cooked off a pot or two of West System by inaccurate measuring of the components.  Quite impressive little polymer volcanoes!  You wouldn't want that happening down in the end of your kayak.  At least with the slow hardener, that's less likely to build heat too fast to dissipate.  I was working w/ fast hardener and the pint container got so hot I put it down...fast...and stepped away while it fumed and bubbled.

just to confirm, have already joined the hull to the deck?

if you haven't, a lot of folks build their end pours prior to putting the deck and hull together so they can keep the end pours as small as possible....they only need to be big enough such that when you drill a hole through the bow or stern for toggles, that the hole goes through the end pour and does not create an opening into the hull.   when you do an end pour prior to joining the hull and deck, you can also add a lots of wood flour to the mix to create a peanut butter consistency end pour which is lighter and uses less epoxy.

anyway, on your direct question about doing an end pour with a different type of epoxy.  i don't think that would be an issue and your strategy seems just fine.  the only point i would make is that you don't need a lot of epoxy to do an end pour if you are careful.

if it was me and i had already joined the deck and hull, i would actually predrill my toggle holes and then cover them with clear packing tape so i could monitor when i pour the epoxy down to only need to add enough epoxy (i would still put some wood flour in for color) to go a quarter inch above the level of the holes i dirllled.  then redrill the hole through the end pour after it has cured.

h

Thank youmummichog and again for your advice, hspira.  I really like your idea of drilling the hole first and then doing the pour so to save on epoxy.  Yes, I have the deck and hull together.

Luckily I have just found a MAS epoxy supplier near me here in Canada, so using a different epoxy won't be nesc.

The manual mentions Wood Flour, as you did -- I have a lot of that and Cell-O-Fill left over... would one be better than the other?  For Lightness?

Also, what size holes did you drill?

Thanks again.

Dave.

for my toggle holes i do my initial drill with 3/4 inch and then i finish it with 1/2 inch which gives me a a 1/8 inch thick epoxy ring in a drill/fill/drill technique.

fwiw, i use spade bits that allow me to have good control of the hole and to avoid tear out.  in my technique, i start with a regular 1/8 inch bit completely through from one side of the hull to the other.   then i swith over to the 3/4 inch spade bit....i drill only half way through and then come back from the other side (using the 1/8 inch hole as the guide) so i 'break through' in the middle and have a nice clean edge.   same technique when i drill through my fill with the 1/2 inch spade...follow my 1/8 inch pilot.

h

   A warning note that probably isn't applicable here after you've received all the good advice above, but maybe will help someone in the future.  I did my first (Sheatwater Sport) kayak's end pours with MAS on a 100 or so degree day here in Texas, using the stand-on-end method, and probably filled the ends with with more than was necessary.  I didn't realize how tough the boats really were at the time, and thought that a good cup full of epoxy in the end would add strength if I ever hit anything at "ramming speed."  The stuff cooked off so hot that it very slightly melted the epoxy on the hull exterior, and maybe caused the wood to outgas a bit or something.  Result was some slight "speckling" within what was previously a clear, smooth outer hull finish.  It looks a little like someone added gold-flake to the epoxy. Neat looking speckles by themselves, but certainly now a "feature" on the boat, if you look closely.  Also slightly roughed up the surface finish, which required light sanding and a fresh final re-coat on the tip of the bow to make that go away.

When I didi the second pour on the same day (I certainly had next to no wait time for the first pour to harden!) I did it with the end of the boat in a bucket of water, and even sat there and stirred the water as the epoxy end pour cooked off.  That worked fine, but even with the circulating water I could feel the wood on the tip of the boat and tell that it was warm, but not so warm as to create any problems.

Second kayak (Chess 17) was done with a mix of about as many micro-balloons as I could mix into the epoxy, and before installing the deck, using a dam.  This time going for a lighter and smaller end pour, based on experience and forum hints.  My one error on one end of the boat was having a leak in my dam, which made a bit of a mess (never to be seen again once the deck went on) and even after trying to add duck tape (wihich doesn't stick to goey, flowing epoxy) I didn't get the leak stopped.  This actually resulted in me standing there like the Dutch Boy with my finger in the dam for about a half hour while I listened to NPR.  The lesson learned on this second boat was to always make sure NPR is always playing on the radio before you get your hands messed up with epoxy.