Interesting Mudcrabdude. Brevimanus are worst for me, although I can't really say for sure because I got my 4 brevimanus all at once from the same pet store. If I had gotten them from somewhere else maybe it would have been different?
Your numbers seem about right Monica. One thing that really helped me cut down on the PPS deaths was to ISO the new crabs at first and try to match the pet store's conditions and ramp up gradually.
Here's a link to an article by Chestersmom on how to do that:
http://coenobita.org/xoops/modules/arti ... .php?id=14
This is how I treat my new crabs from bad conditions to prevent PPS:
Basically, you should determine the conditions at the pet store and try to match those in an ISO tank with shallow substrate so the crab can't dig down immediately. Then you raise the humidity by 10% every 5 days until the crab is at the appropriate levels. Then you give the deeper substrate so the crab can dig down if he wants.
For example, suppose your crab comes from a bone dry tank with no guages. You would then try to guess the humidity. In my part of the country, its usually about 50% relative humidity.
So this means that I would start the crab out in an ISO tank at 60% and 72F.
In 5 more days I would increase humidity 10% to 66%.
If in another 5 days the crab is looking good, I once again increase it 10% to 72% and up the temps to 78F. Now the temps are where they should be. Another 5 days and the humidity will be in acceptable ranges too and only then will I add enough substrate to allow the crab to dig down. By this time, he's beefed up and adjusted well so he has a chance at success if he needs to molt.
I've hardly ever lost a crab from bad conditions when I've used this method. But I haven't yet figured out a method for pet stores which have good conditions since I don't know what kind of conditions the crabs were kept in at the supplier's. After they've been at 80/80 at the good pet store, I didn't want to jerk them all the way back down.
But this time, I'm not taking chances... 
Probably what stimulated it to eat a lot in the first month I got it and has fasted since and now has been showing premolt signs, I think...). But still it outlasted my perlatus......... 
