Hmmm... I haven't heard of the Hennemens principal, have to look that up.
Whats worked for me is training arms with opposing muscle groups, chest with bis, back with tris. Then they're pretty fresh after you finish your major muscle group.
Also, something that works really well for me is cheating the weight very slightly when training arms. I'm all about good form, but this seems to be the only place that some extra body language helps. For example, if I can curl 30lb DBs with flawless form and 50s pretty solid but with poor form, I'll use 40s. I will do the first 4-6 reps 100% clean, then maybe use a little cheat to get the last 2-3, but also contracting as hard as possible at the top and doing a slow, controlled negative. Hope that helps