from what I've found (at least with my own work), is to figure what the biggest file you might need for your uses (whether current, or down the road a bit) are rez-wise. and go a little bit beyond that.
say, if you needed to reproduce a 11x17 document at 600dpi, scan it at 900/1200dpi. you get a bigger file, but if you need to go just that little bit bigger, just if; you won't have to re-scan or sample up(sampling up is never an option in my case, just a great scan)
being that you have 8x10 negs, these will be big files, especially at 16bit, so double the space.
I would scan in RGB 16bit, even if you only use 8bit. Just in case. Or, if you know for certain you WON'T need 16bit for certain negatives, scan in 8bit only. If you're unsure, go with 16bit.
wet-mount(have you considered this)? I know one person who uses an IqSmart3 scanner, and he ALWAYS wet mounts with Kami fluid and AZ42 overlay. He shoots 4x5 and 8x10, and if you want pixel peeping, check out his files .
wet-mounting takes more time, but IMO, its worth the time and effort.
just so you know, I scan everything at 16bit. I figure that HD's are cheap, and backups can be made plentifully. With the price of storage what it is right now, I figured, what the heck?
-Dan
