Yes, a definite improvement over the stock Sabre. Night and day.
Don't know why your A7 won't fly, that's weird! Maybe you just got a bad engine. I think you must have gotten a particularly GOOD engine on your Sabre! Or maybe it just needs more time on it? Mine seemed to pick up a little speed as it got more time on it, but the first flight, after only minor, sloppy, two tanks of break-in, flew fine.
If you think you have a lemon, let me know, I have a spare Toki engine(no fan) you can have. You could also put just the engine into your Sabre, a friend of mine did that and got a nice boost. Just the engine change requires very little work. You will have to find a header, though, as I am shy one header. Standard car headers will fit.

Some more stuff on the A7:
I did not use flaperons. No need.
It needs some throttle for landing, otherwise it will bounce like a Kangaroo on cheap struts.
Doubt if it will get off of grass with those cheap wheels.
Stock control throws were perfect.
Duration is a bit short for my tastes. Comes with a four ounce tank, good for a five minute flight with reserve for a go-around or two. I could fit a larger tank.
There is a slight trim change as the fuel, ahead of the CG, burns off.
It balanced with zero ballast, right on the money.
It would be a great way to get your feet wet in jets without spending an arm or a leg or a lot of time.
It is still a jet, and would be a lousy second airplane.
The stall is a non-event.
Retracts are a possibility, though you would either need to find twist and turn retracts, which I do not think exist in this size, or use very small wheels, to keep the wheels from protruding into the ducting. I think retracts would up the speed a bunch. The plane seems to hit an aerodynamic wall.
55 mph is a total guess on my part. The only other jet flyer witness was Vinnyjet, maybe he can chime in with his impressions.
It's FUN.
It's RELIABLE. Seven flights, not a hiccup from the engine, zero maintainance.
I think if you swapped out the Toki engine for a hotter one, things would get even better.
Again. It's not fast!