I'm on the 488 as well and I use the tdk SM series secifically the sm60's. I believe that they have a slightly more stable mechanism and slightly thicker tape stock. They are availabe at Guitar center and I'm certain that if you did a google search will find other sources as well.
ABSOLUTELY DO NOT use anything above a 60 minute cassete. The tape stock in 90's are thinner and are prone to stretching and print through. They also can put excessive wear on your motors. I do not know if you have the manual or not but it speciffically advises against using 90 minute cassettes. If you do not have a manual get one, YOU WILL NEED IT. They can be ordered through TASCAM for about 20 bucks.
No problem. I had to wrangle with that machine for a while before I could really use it. I started recording about only a year and a half ago on a 488. I'm just now starting to get a little frustrated with it's limitations but i don't think that I've outgrown it just yet. Nice to see others using that machine.
I like the picture of the guy that looks like Donald Fagen getting blown across the room in his Lazyboy by his speakers. Do they still make those maxell's? I have'nt comparison shopped for cassettes in a couple of years.