it seems to be a pretty cost effective way for me to go. i have a blackface showman head which i adore but i'd like a more compact option for smaller gigs and sessions. a blackface twin is way too expensive as well as not being much more compact than the head with cab setup.
Try JD Newell cabinets. He'll make you whatever you want. Reasonable prices. I'm doing the same thing as you with a '66 Fender Showman head, but with a 15" JBL D130F speaker. Give him the dimensions of your chassis. Addy is: