RE: Sig four star 60 or 40
Either the 40 or the 60 is a great choice. $$$ will be your deciding factor here. Ask yourself this, do you want to transplant the engine, receiver, battery and servos from the trainer or are you going to go with all new for the 4*?
If your trainer is a 40 which most are and you want to transplant then the 4*40 is the answer. If money is an object for a completely new setup, then the 4*40 is the answer as it will be cheaper then the 4*60 in all respects. Both planes work well with a basic 4 channel non-computer radio.
Once you do the first landing all the nervousness about taildraggers will go away as the 4* series are all *****cat's at heart, but with the proper mods can be really made to get pretty wild.
Even though I've moved past my 4* 40 in most respects, I still keep it around to burn holes in the sky with. I used to have a Saito 56 on mine but engine problems forced me into an OS46AX and that engine with the APC 11X7 prop really makes that plane scream. The Saito did well but was a bit slower on speed but with a 12X6 Zinger prop it pulled it around without ever breathing heavy. The OS does drop rpm in violent maneuvers (even with an APC12.25X3.75 prop) but the Saito just keep chugging along without hardly any drop in rpm.
My recommendation is if you want flat out speed the a 2-stroke will be your better bet. If you want to swing bigger props with huge amounts of torque then a 4-stroke is the way to go. Personally I like 4-strokes for the sound and fuel economy.
Here is an old picture of mine right after I did the maiden. Bugs Bunny is now the pilot with a tinted canopy and even though it has never been crashed it is showing the effects of 150+ flights on it.
EDIT: This pic has the Saito 56 in it turning a 12x6 prop and after the maiden I added the white wheel pants which after the tinting really dressed the plane nicely. Guess I should take another pic of it. I also took the canopy and turned it around, then cut it on the big bump that is near the middle which lowers it and gives the plane a more sportier look. Basically you will be cutting the canopy in half accross it's width, not length. Works well on all 3 three versions on the 4*'s.