As said it should handle any speed on the road you care to travel as long as the angles are proper. A High-Angle shaft is not there specifically so you can run at extreme angles all the time, or to correct for an improper pinion angle. It's simply to allow you more leeway in suspension travel before it binds.
Nothing inherent in it's design to limit your speed that I know of.
Good product. We sell them too, for that reason. I think we stock one for the front specifically, but obviously they can make you anything you need I would think.
What's your setup? Got pics.
Keep us posted on how it all works out.
Paul