The Brodak Pathfinder kit is pretty good as supplied. Watch your weight build-up, Use a good 4" bell crank, strong flap, and elevator horns with quality ball links and carbon rods, and you should be good to go.
If you want to do what Gordan has done lately, add about an inch to the top of the vertical stab.
The Pathfinder 60 that Gordy folded the wings on was not one of Brodak's kit versions, the Pathfinder Mk2.
The earlier versions of Pathfinders had a faux I-Beam construction where the 1/8" thick I-Beam was slotted, top and bottom, to allow a locate, twist, and lock, method that made building the wing easy. Unfortunately, it proved to not be as strong as it needed to be under rough conditions. Gordan's wing folded while doing what appeared to be numerous 10-foot dia. loops, both inside and outsides. He was flying it like a combat ship, probably trying to see how tight it could turn I think. After about 30 or so seconds of this flogging, the wing folded in a bang.
The First one published, The Pathfinder PRO-file (Flying Models and kitted by Smith in Calif. (200 kit run, and rare), as well as My full-bodied version The Pathfinder 40, (never published), and the Pathfinder 60, for lack of a better name,(also never published), all used this style of faux I-Beam wing design.
This failure caused Gordan to revise the design to a "C" tube wing. It was renamed Pathfinder Mk2 and is the one Brodak is kitting. As far as I am aware, there have been no failures with this version's wings as designed. Going to spruce spars may make for good feelings, and will be stronger, but adding weight to the design, carried to extremes, will ensure it might survive a crash, but it likely won't fly as well as it could have. Keep this in mind as you build your kit
If you feel you need stronger spars, laminate a .006" Carbon Fiber strip between 1/8" balsa strips. They will be lighter, and stronger than Spruce if you do it right.
Enjoy your build. Do it well, and you'll have one of the best flying Stunt Profiles that are currently being kitted.
Fly and have FUN.