If the OS is OS/2, then of course do, if possible, use up to 2 GiB RAM as RAM instead of using RAM as swap file space. The OP should probably use the HPFS drive, drive 1. Swapping should be a rather rare event.
Nevertheless: if you aren't using r:\ as a TMP setting, then does the OS create r:\TMP and r:\TEMP after a reboot, or may it be worth the efforts to create (and preferably hide, e.g. to avoid getting DELTREE'ed) those TMP directories?
Assuming normal usage instead of just managing huge ZIP files by appending small files frequently, when is the speed gain of using a RAM disk for TMP the most impressive?
What's a recommended size, e.g. to account for large 32-bit files? As large as about the largest ZIP file you've got?
A known advantage is that any reboot will clean up the directories, albeit cleaning software could delete even more files. And I tend to use a RAM drive when software does access the same data file a gazillion times (ZIP file password guesser, quick & dirty Rexx solution, ...), to avoid Microsoft's physical harddisk torture.