I think I would have made these out of 2 x 10's with a 33' LOA.
I stayed away fro any lumber over 3/4 of an inch.
The expansion and contraction from heating and cooling of wood under 1 inch is the same as the epoxy. If you have timbers larger you may create possibilities of delamination.
Any defects in a single piece of lumber is lessened by having several pieces laminated togeather. If you have just 1 defect in 1, 2X10 you could loose the whole timber.
OK. . . . . .