Here is the response I got from Vectorflight. It was fast but they understandably took the high road. Unless I hear from others who have put a 4-stroke 120 in there, I will probably just scale down to the 91 size: C'mon anybody put a 120 in either the Edge or the Extra?

Dear John:

Thank you for your message. A 120 is bigger than the recommended range for
our 66 inch wingspan airplanes and we do not have any personal experience
with such. However we do have several reports from customers who have used
120 4 strokes and 1.08 2 strokes. There are several issues to consider when
using an oversize engine, for example the firewall and tailplane in
particular should be reinforced to absorb the extra stresses.

A Dave Brown FS 120 engine mount is available at most good hobby stores,
which will fit into the existing pre drilled firewall mounting holes, with a
little coaxing. The supplied engine mount, a Dave Brown FS90, will be
undersized for the 120. The Edge is more suitable for a heavier engine as
it has a slightly longer tail moment which will help to counter the added
weight in the nose. Reportedly both airplanes have been flown successfully
with these larger engines. The extra weight may also require adjusting CG
and control throws so that the airplane is not prone to tip stalling.

The current published lead time is 2 weeks, although we are beginning to cut
it down by a few days at this time. It will still be at least 10 days
before we can ship an airplane out. We do apologize for this inconvenience.

Please let us know if you may have any other questions. We will be haply to
provide as much information as possible to help you make a decision.

Regards,

C/S
VF