These boats are lightweight by design. I have read that the nails are not required, just use lots of straps to hold down decks when curing. As far as planing down the shears, you are going to do that anyway to get the correct bevels for deck adhering. If you are alluding to using less of a shear, you are giving up structural integrety, not worth it IMHO. Use less goop when making fillets and building smart will make your boat as light as you want it while still maintaining the required strength. Good luck.

Eliminating the ring nails will save you 4 oz.  Some straps and clear /tan packing tape and lots of care will get the deck on.

The sheer clamps can be planed down to a triangle cross-section.  That will save you the weight of one sheer clamp.  Weigh yours once they are scarfed together to see about what you will save.  There is a slight loss of strength from the loss of wood mass, but it shouldn't be significant unless you intend to paddle in demolition derbys.  I think the primary purpose of the sheer clamps is to help hold the deck on, trimming away the inside corners (after they're epoxied to the sheer panels) won't affect the deck-gluing surface.  Makes it easier to coat the insides with epoxy, too.

I have some 16-ft long shavings from sheer clamps.  Make sure you keep your plane's blade sharp!

Lots of care with epoxy, fillets, glass work and cleanup will save more weight.  So being careful and patient is one of the best ways to save weight.

Best of luck on your build.