The vardiff on our MPOS pool was set like this; I honestly wasn't sure what our p2pool is set as. I'll be sure that the vardiff is set as suggested. Thank you.
The problem with setting the min-diff that high is that there are still a significant amount of miners that mine with less than 1 MH/s out there on alt-coins. There are very few people that mine with paid-miners or have large rigs. I have set the starting diff to 128, and the low end to 32; however many times people don't understand why they are not submitting shares with their GPU.
P2pool doesn't have a vardiff strategy, it simply has a set share level relative to the difficulty I believe. Ergo, anyone with low power will likely submit few shares and those with big miners will see a good amount. If you're worried about paying for miners and mining on the pool, then point them to the p2pool address, otherwise I'll likely leave the Stratum stuff set as it is. Keep in mind, p2pool is LONG-Poll.