sourcing more small triangles of metal should be doable. Maybe ask TG if they will sell you another 6 pack of just the gussets.
I question if cutting off and re-welding the sliders is necessary. How hard core will your off roading be? If not heavy bash rock crawling I say you need not go through the hassle and expense of removing/reinstalling. I'd cut 6 more triangles from the frame plates in the kit then weld 2 per leg at 9 and 3 o'clock.
I don't know how hardcore. But I'll sleep better knowing it's stronger then now and won't have to worry about anything if I do end up off roading hard. You know ? I'm gonna cut them of and re weld it to the plates with chasers. I think I found a set of 6 just gussets. Thanks bud