Digital BW, The Print

I cannot afford to purchase one of these Polaroid 120 film scanners 
but a local photo equip rental house has a unit with Silverfast 5.2 
available to rent on a daily basis - I have a mountain of black & 
white 120 & 35mm negs to scan.

Can you offer any pointers to help me get the very highest quality 
scans possible ?

One thing I searched the archive for but I didn't turn up any 
results  - apparently there is a way of keeping the film flatter 
(particularly the 120 negs) for a sharper result ?

I guess I should scan 16 bit not 8 ? Comments ?

Should I scan in 256 greyscale mode ?

I'm using Photoshop6 & Windows98SE

Thanks
Frank