There are some folks who just love Rodinal. I'm not one of them. For me it's just another tool in the box. I use it sometimes, and I've tried it with a lot of different films. I've even used it at 1+100 as a stand developer with some success on fast films when I wanted to get a lot of grain. What I don't see with Rodinal is full emulsion speed. If I over expose the film by 1/2 stop or more, everything is cool. If I try rating the film at box speed, it's no soap. This tells me that it's not going to be very good as a push developer. If anything, the shadow areas will be more devoid of detail than if you'd exposed the film at box speed.
If you must rate HP5+ at 800, you might want to try Diafine. I've done this a few times when working in dimly lit rooms with a moderate power flash and a relatively slow (f/4.5) lens on a press camera. It worked better than I'd expected. The negatives were relatively easy to print without too much dodging and burning.
I can't argue with results.