You don't have to move the temp files to the RAM drive if you don't want to. I run a video game server on mine for slightly faster use of game files for people that join the game, as well as few other things. This way my HDD isn't being constantly used either.
I also use the RAMDisk software, and ended up buying it to make larger RAM drives than 4GB. If you just want a 4GB one, you can use their free sample version that will let you use up to 4GB.
Of course you'll likely want to backup what you have on the RAM drive in case of a power failure, and so on.