Personal preference............ 

Go forthe boldly. 

they don't provide measurments so you can customize it to how you want it.

that said, there are a couple things i keep in mind...

•  the deck pattern is an important part of how the boat will look....so take your time.  you can use blue tape to test out your ideas (see picture below)
• there is some functionality....things like a place to hold down an extra paddle or a water bottle.  so in addition to the blue tape to plan it, i will make sure it can accomodate things like half a paddle, a standard water bottle, a map, etc.
• there are safety elements as well....so i always put a perimeter line on my boats.....they are otherwise very slippery and hard to hold onto.  again, i plan this with blue tape. 
• depending on how you attach the lines, remember the difference between where the hole is in the deck for the fitting vs where you wanted the line.
• remember to understand where bulkheads and other behind/underneath the deck things are so when you plan your holes you can actually attach your fittings (e.g., not right on a bulkhead, with enough room to get a bolt on the other side of a screw...placed in a place that you can reach with your other hand through a hatch if you expect to attach it after the hull/deck is assembled.

below is how i did my shearwater 17  and another boat in the planning stage.

hope this was helpful.

h

Keep in mind, too, that while the bungees need to be stretchy to hold down your deck implements and cargo, the perimeter lines should have no stretch at all.

Laszlo

   And, if I might, while esthetically, tight perimeter lines look nice, they won't help you getting back into the boat if you can't get your hand under/ around them, especially if you're wearing gloves.  Leave them loose. Use your bungee cord for "deck cords", but a non-stretch line around the perimeter. Have fun in the rock pools.