I am sorry to say that all the code is written for the PPC as to be cross compatible with the NG Amigas. But the A4000 is an excellent platform for OS 4.1; even a 604e at 150MHz shows it to be a quick and modern operating system. It is very compatible with legacy 680X0 code by bypassing the jit compiler and passing it on to the 68060 -- something the NG's can't do.
Hyperion has a forum for Classic Amigas running OS 4.1 that has a lot of information (check Hardware Compatibility, for example).
