If you haven't already looked at it, is the photo of off HPN's site. There are a few people on the web (mostly through Mica peak's web loop) that have old HPN race bikes or have paid for the modifications; you could likely find some better photos there. I braced my frame myself, and found it easy and effective. The main areas of weakness are in the rear subframe, extra struts from the rear footpeg mounts to the rear of the frame help the most. I also welded gussets into the front frame, tying in the frame tubes around the steering head more tightly.
I think you really need to answer the question of: Do you want an off-road racing machine, or a travel bike? The HPN modifications are nice, but have you looked at the seat hight? One of the modifications that they do that makes lots of sense to me is the lengthened rear swingarm, which gives more suspension travel.
I think Grant's advise on using mild steel for frame and rack material is wise - easy to work with, ductial, and easy to repair. You gain a few pounds over more exotic material, but for a heavily loaded overland bike, this is not the best place to save weight.