Again with the "no mantlet cover"!
Make one out of epoxy putty! It ain't hard, really.
You'll also get a better prodct than most kit equivalents _and_ you can position your gun tube in elevation exactly how you want it before you create the cover. Can't do that with the kit ones.
If they produced one in the kit we'd be complaining about how hard it is to clean up the seams, how the joints don't fit properly, how it really doesn't look like canvas, and how we really wanted to elevate the gun a tad more than in the kit.
I _don't want_ the kit makers to make the canvas covers. They _never_ look the part and they restrict how I can present my model.
Epoxy putty is your friend, embrace the putty!

Paul