In flight Diroama (Me 109 vs P-47)

You could pose them together as "adversaries", instead of trying to depict a dogfight. I did a P-40 and Zero that way with brass rod.

Boy, Bondoman's right here.. You'll have a helluva time getting it to look right with both aircraft in the same scale.. This type of diorama is best depicted in a shadow using mixed scales and forced perspective.  Suspending the aircraft is especially tricky, you'll see the rod/wire/string no matter what, so you'll need to restrict the viewing angle using a shadow box window... That way you can hide the suspension system for the view and control the angle and lighting...

I'd suggest getting copies of  the "opponents" in 1/72 scale (even better,  1/144) and doing both of them from opposite perspectives...

That way you can do bth 1/48th kits, and you don't have to be locked down to the "earth" being at the bottom of the box and the "sky" above.. You could have the "earth" at the rear of the box, on top, on either side, whatever...

I buy acrylic from TAP Plastics. You can find them online. I wouldn't be afraid to make it pretty thick, either.

A more general question... it's a challenging diorama if you have both aircraft. If you plan to have them in pursuit, the scale will get you. Even a couple hundred yards translates to around a dozen feet at scale.

Other more manageable options would be one flying over the other while the loser is bailing out, or a head on convergence (pass).