SafeTwire,

No worries, I will re-inforce the mid section. You are right, it is a good precautionary measure.

I usually use finishing resin for this type of work since no thining is needed. And to follow your train of thought, why risk it if manufacturer's advise against thinning .

The chemical reation that cures epoxy is exothermic, which means it generates heat. When you mix larger quantities of epoxy, more heat is retained, which accelerates the reaction and causes even more heat. As you noticed, larger quantities greatly affect cure time. When I need larger quantities, I usually either mix multiple batches, or spread on a larger flat surface to better dissipate heat, hence maintain cure time.