I thought the chemistry was more complex than that? The chain propagation is also radical based as the catalyst is just a radical initiator. If so chain entanglement is causing the gelled state and the cross linking is radical termination. The whole thing is a ballancing act with catalyst loading. Polymer chemistry is nuts, lots of maths involved which is why I went towards drug discovery.
Thinking about the warping issue I suspect I've escaped it so far as I always add bracing panels / flanges to my moulds. This coupled with my slow lay up has probably been lucky for me. The shrinkage is an odd on too, I have a car bonnet / hood that fits back into the mould. Even after 3 years! Is this because I'm a hobby moulder and tend to demould a week or so after the final layer?