I am about to start the build of a Sig Something Extra, during which I plan on making several modifications.
The first one is to build the Horizontal Stab and Vertical fin as airfoils and eliminate the guy wire supports. With the flat slab surfaces I can see where they may be needed to stiffen up the tail feathers. I feel that I can build fairly ridged airfoils that should not require the additional support of the guy wires and eliminate some drag in the process.

Do you think that they are needed when using the airfoil shaped surfaces? Your thoughts/advice?

After having read several of build threads here I am going to increase the size of the rudder and elevators. As far as the rudder I am thinking of adding about 3/4 to a inch to the overall width. Now for the elevators I am thinking along a 10/15 % enlargement of area. Using both a larger counterbalance and a bit more depth. Your thoughts/advice?

I am also going to eliminate the cheeks and use a full cowl with an inverted engine mounting. The exhaust of the engine heat will be located near the leading edge of the wing. One of the major reasons for the cowl is both to reduce the drag and to increase the frontal area for better Knife Edge performance. Your thoughts/advice?

Also I plan to to add fairings to the wing fuselage joint area. For this I was thinking of using 1/2 to 3/4 inch radius. And add about 3/4 of an inch to each wing by adding horner style wingtips, the thought here is to reduce the chance for aileron flutter,as well as reduce the chance of tip stalls at lower airspeeds.
Your thoughts/advice?