There is a lot of information on end plates from Ed Moorman on this site that suggests the end plates will help with roll rate and stability. Those plates come off easily with 2 2-56 screws. Can fly with em on or off real easy. They are real light too. 3/16" balsa.
I don't like the round wing tips look, and Ed's research shows they are one of the worst aerodynamically. So that made it an easy decision to cut them off. But with the wingtips flat, it didn't make sense to keep the stab rounded so I left them square also. I like the look with squared off better. Just a matter of preference.

Pics of the aileron set up. 1. Servo set up with star horn for differential. 12% on the low end and 45% on the high end of the throws. 2.Bottom of wing. You can see the bellcrank through the slot. and the pushrod. 4-40 bolt connected directly to the bellcrank. 3. Top veiw of wing / bellcrank. 4. Top view of wing / bellcrank. 5. Pushrod through wing. 6. Flap set up.

Believe it or not, there is zero slop in the ailerons. I was very surprised how tight yet smooth they operate. And the ailerons move identical to each other. I used a protractor set up on the control surfaces to measure accurately.

great job!

I will start building Mid Star pretty soon.
What kind of engine did you use?