fwiw - da30's are NOT compatible with 90m tapes without tricking the machine
I'd stick with a da20
Tricking the machine is not a problem. Paul did that to mine when I had it serviced 3 years ago.
The other option is to put a slice of tape over one of the holes on the back of the tape cartridge, which isn't a big deal either. I'm sure its an easy mod to do what Paul did.. he didn't charge any extra to do it when he serviced it, so it can't be too involved...