CForest first version

Sorry about the (void) convention in functions, this is what happens when you copy and paste ignoring the other changes :)  Other RRTstar tweaks have been also overwritten.
Let me see if I understood properly. You are talking about generalizing the CForest for planners in which there are more than one tree in each planner? I do not know if this is even possible with the current algorithm. Actually, I would say it is out of the scope of the current published version of CForest.

I guess you are talking about start Motion and not start states, to get start states is not difficult.

In other words, I do not know what you mean with this comment. An improvement to pruneTree()?

Also, I see 2 problems to the solution you propose:
1. It is not possible to apply that threshold. Once the planner is approaching the optimal solution, prunes just take away few nodes. Therefore I first check how many nodes would be pruned and, if worthy, do the prune. Not possible recursively.
2. I read that recursive functions have poor performance in comparison against loops. What I do now is more or less what you said but assuming only one start state.