one Rocket ... was a 33 MHz 040 but I remember putting a 40 MHz chip ... into it.

Click to expand...

8-o You know, that never occurred to me. I've got a 25MHz Rocket here somewhere - might try it myself.

If you check my blog on AF, there's a link to square wave oscillator ICs which can be speed controlled by a serial data signal or a pot. One of these would allow you to tweak till you find the exact best stable speed.

Otherwise check Output Enablers