A what!? A 7x17cm?? That sounds odd and no doubt it would present a problem given that the Epson trays only support the 6x17 size, so you're losing the tops/bottoms? Most educational. I wonder if Boots the Pano Man knows about this obscure format...
A quote of $30 for a 7x17cm drum scans sounds strangely appealing; the end result would be a 70-80Mb for a smallish print (I know one photographer shooting 6x17 and 6x24 who ends up with a 700mb file!!); how big is the file size and intended (300dpi) print? I scan at 4800 then downsample to 300dpi for despecking (6x7, 30x25cm output).
I'd like to eyeball your 7x17cm; is it a home made Wallace and Grommet or a pro-level get-up. I don't have a pano at present; it's having surgery for focus anomaly.