Brandan
This is the way I stretch my frames.
I glue the strip inside the frame and let it dry.
Then I fill the gap on the out side,after it dries I shape the out side to match the frame.
The inside strip will halp keep the frame from breaking so easy,I have dropped one myself and it held with out a problem.
As far as inside overlapping pass your cut frame a least a 1/4 inch at both ends works good.
The frame in this photo is 1/16 scale so I overlaped it for the weight of the model to keep it from sagging.
Once I get the out side shaped I can post another photo on here.