I won't answer any overclocking questions. There is only one answer: Don't do it.
Over the years, I've had an enormous amount of support eMails where I was trying to help customers who had instable Amigas. It turned out that almost all of them had Apollo accelerators, and that none of my products was the cause for the instability.
One day I decided to put an end to this and bought the rights to the Apollo accelerators. Further, I changed my policy about Apollos: No guarantee to work with them in any config. I will not give any support for Amigas with Apollos.
This is purely a stability policy. I've been verbally attacked a number of times for buying out and shelving the Apollos, but I think I did a good thing for the community. If someone has flaky Amiga, he will lose the interest sooner or later, because a randomly crashing Amiga is not fun to use. It's more like a reason to quit the hobby, and that's what I wanted to avoid.
After years and years of Apollo-bashing from my side, the only way for me to bring out an accelerator is to make it rock-solid. To do that, you need to operate all components within spec, and memory is a critical component. The CPU can easily take 20% overclocking, but memory can't.
Cosmos, you claim it's stable, but you cannot know that. "Proof by example" is not a scientific method. You operate the components out of spec, that's the only scientific data we have here.