I'm a bit late to the party on this one, but:
tezza wrote:I've read that good quality 48TPI soft-sector disk can be formatted to 96TPI (quad density) and may work ok even though they are out of spec.
If you're talking QD then yes, it should work fine. Back in the Sord M23 mk III days most disks available locally were DD but the Sord used 100tpi QD drives, the DD disks were just fine and still are 30 years later. The disks from dad's era programming them are a mix of 48tpi and 96/100tpi and all have read ok. The drives are another story, which is why I always say I'm interested in *anything* Sord on the off-chance I get some more FD-20 dual floppy drive units! I understand the drives in my CBM 8050 are the same but I still haven't had a change to power up my 8032 and 8050 up yet.
Note that HD is a totally different story, but I think everyone knows that.