I have nothing against smaller bikes, I used to preach loudly that they were a lot more capable than people give them credit for, but I could not go back to them for gravel road work.
Just can't imagine a loaded small thumper keeping up. On single track? Sure, but I thought we were taking about dirt roads, steep ones at that? There are smaller light bikes that definatly will but they are high performance bikes that get away from what I consider a dual sport. They are more like plated racers not able to with stand long pavement . Ive only heard comparison to the DR 650. Not many higher end bikes. ( Husky, Ktm, Husaburg.....) Ive ridden and ridden with small thumpers and on twisty single they left me, but on steep rough or dirt road? If you cant maintain at least 60 on pavment I doubt you will on dirt.