Sure.  Qimage can print well beyond 39 inches but since your printer will only allow 39 inches per page and it doesn't support roll printing, you'll have to splice anything longer than 39 inches together.  For example if you print (say a multi panel print) that is 60 inches, you end up with two "pages" that you have to splice together.  There is physically no way around that: since the printer/driver doesn't support it, Qimage will do the best it can given those physical limitations.

Regards,
Mike