I think I know what this is. The issue is not the need for the 32 bit hook proc to be injected. I suspect that works. The problem is that once that 32 bit dll is running in the hooked process, it cannot send a message back to powerpro.exe in the case where the hooked process is running at user level since powerpro is at admin. That is what uipi limitation is.
There is a way around this by calling a windows api function from powerpro.exe which I may look into adding on the weekend. This won't fix the 32 versus 64 issue. I don't know any easy way around that. I suspect I have to create a 64 bit version of the ppro hook dll and a 64 bit program to load it. Not something I plan to do at this stage. Do PowerPro mouse hot keys work for you, e.g can you define right click on caption to close. Try on both 32 and 64 bit programs.
