Hi Chris - you can find some technical date sheets that show the T-glass, E, and strengths that are available as a pull down in most of the MGS supplier sites (AC spruce, Wicks, etc). There can see the material changes when cured at both elevated temperatures and for different time durations. Really, do go with what a few others have said - the manufactures temp. At some point - refer to graphs, the increase in time will have very little effect at a constant temp. What you should pay attention to is not going to the extreme cure temps that the resin is capable of - then you could end up with a section of the boom with strengths and flex characteristics that vary from the original build. Basically a very stiff section between the original boom sections that will cause stress problems. And then it is a repair - easy to make stronger without much effort! I assume you have it in an alignment jig - it would be wise to keep it aligned as repaired and supported during the cure time.
Regards, Mark