Cluster Config Question

Hello OpenMosix users -

I'm in the early planning stages of setting up a SSI cluster. I've read the
OpenMosix Howto and also the FAQ, but I couldn't find a good answer to this
question and I hope someone on the list can help:

We have about 10 systems running 3 different versions of Red Hat Linux. The
versions are RH 7.2, RHEL3 WS, and RHEL4 WS. I know RHEL4 may be a problem
because it runs the 2.6.x version of the Linux kernel.

My question is, how similar should the nodes be? Is it ideal if they are
identical? Is it a problem is they have different applications installed on
them? Most of the nodes at least have the same NFS mounts for storage
already. But how does MOSIX deal with an ImageMagic process, for a random
example, starting on one node that has ImageMagic installed, but then the
process migrates to a node that doesn't have that app installed?

I also read that people shouldn't expect big speed-ups on compiles, but
compiling is only part of the workload for these clusters. If compiles still
work, and other loads can be effectively load balanced, compiles should
benefit as a side effect. The question again comes down to, differences
between the systems, are they okay? What happens if a compile starts on one
system and then moves to another that doesn't have some required libraries
or has a different version of GCC?

Any pointers greatly appreciated! Thanks. -Brian