The Fender Deluxe VM is a great amp which needs a better speaker. Unfortunately very few will fit. There is a simple answer though.
I've recently replaced the stock cheap celestion in my VM with an Eminence 1218 legend 121 by simply undoing the six screws holding the baffle in place and moving it forward by 10mm. this gives sufficient clearance for the Eminence and probably quite a few others. The only other mod needed was cosmetic. By moving the baffle forward ,a gap formed between the control panel and the baffle. I simply sprayed a 10mm hardwood quadrant black and glued it to the top of the baffle - no gap and very difficult to tell anything has been done.
The complete mod only took an hour, the amps sound is transformed. Much more bass response and clearer sound. Hope this helps someone