My theory is to have the same wing area, wing span and the same lift/drag. I guess one would have more lift at the root and the other more lift at the tips. My goal is to have a wing that's easier to build but will perform just as well.
MM
The wing's contribution to the airplane's L/D is more a function of aspect ratio than anything else.
The taper makes the wing a bit more efficient, but given the way we torture aerodynamics in stunt I wouldn't worry too much about it. A tapered flap on a constant chord wing is fine. Just remember that if you taper the flap and not the wing thickness towards the tip you add aerodynamic twist into the wing as you have a constant thickness and varying chord. Still, it works just fine. A Magician or an Oriental can tear up the pattern. Sneekers had constant thickness tapered wings and flew just fine..and fast too!
In the end, in stunt I believe a lot of conventional/mainstream aircraft design is really not applicable. (IMHO) We're not looking for speed and efficiency. We're ( well, at least I am) looking for the best balance of maneuverability and smoothness.
I guess one can argue that the tapered wing will have less drag in maneuvers...
Anyway, take the span of the original tapered wing, square it, and then divide by the wing area. That's your aspect ratio. If you keep the same wing area then you can rearrange the same formula to replace wing area with chord times span... This will allow you to solve for the span or chord you need for the constant chord wing. You'll now have a constant chord wing with the same area and AR of the tapered wing which should have roughly the same drag due to lift as the tapered wing. If it were me I'd add 10% to the AR for the constant chord wing vs the tapered wing to make up for the loss of efficiency (as in Oswald for all you engineers out there).
If you really want to get into it, since the MAC is not (usually) the same as the average chord on a tapered wing you'll need to know the MAC for the original wing and then place the constant chord wing on the fuselage to maintain the same tail volume coefficient.
But the main thing is don't get too hung up on formulae and airfoils and all that. If it looks "right" it will probably be just fine. I've always believed the best stunt ships were eyeball engineered and then refined.
All IMHO and HOMV (Howard's Opinion May Vary)
Chuck