The stab reinforcement is not needed. The stab is short and it's sheeted. I have done some blenders with mine that were a blurr. The stab has never gave way. The stock cabanes are plenty strong. It's the mounting areas that need help. Either glass the tabs in the fuse before you sheet the front deck or use a ply doubler. Or both. I have never broken the tabs but the bolt pulled through, washer and all. The ARF I fly now is doubled in this area.
Also read a thread by Fallingleaf in this section called "Goldberg Ult engine selection" or some thing close to that. I will find it and bump it to the top. There is a lot of good info there on the build and on the installation of dual elev servos.

David