Hope you are still monitoring this thread. I face the same issue here. And I'd love to be able to move gMail and Browser to the SD card. I cannot because these are pre-installed apps by t-Mobile. There's no way to move those -unless- you root your phone, right?
It's funny but about 8 weeks ago, I had to do a factory reset. I imported by backed up data and after all was said and done, I was surprised to see 103mB of Phone Space available. I thought, "Hey, this is great!". I did not install additional apps but waited a while because I didn't trust it. And, gradually over time, the Phone Space (internal mem) decreased a bit when I checked it. And now it seems to hover at about 40mB. I use Android Assistant which does the same types of things that Cosmos does (I think).
So, without me installing everything else, "something" in the phone chewed up about 60mB and I don't know what did or when it did it or how to reclaim it (except by doing another factory reset?)
H