I decided that I didn't want to cut up the cowl on my shoe either, and after some research, found that a Tower .75 would just fit mounted horizontally without cutting the cowl. Am running a Bisson pitts style muffler which has a nice throaty sound, and gives good pressure to the tank. Only holes in the cowl are 2- 3/4" x 3-1/2" slots for the muffler which have not given any cooling problems so far. Have been very pleased with the Tower (my first one) and has been radared at 96 mph running an APC 12x8 with 15% nitro. I did some reinforcing mods to the fuse which made it come in at 8 lbs. Have about 40 flights on her and am very happy with the way it flies, on rails, but will do very nice axial rolls, inverted flight is very stable. If you want your plane to hold up, I would advise reading some of the threads on the SS which describe how to fix the belly area and landing gear plate which are the only weak areas on this ARF. I replaced the very flimsy 3/16 balsa stringers with 1/4 spruce stringers on just the underside, and reinforced the landing gear plate with triangle stock embedded in wet glass and cloth on both the upper and lower sides. Also reinforced the wheel pants with a couple layers of 2 oz. FG and made the plywood plates larger to spread the load out. This thing is bulletproof now and has come down hard a few times with no problems. One of the best, no, the best ARF of the 20 I have put together and flown. Just do the mods as described in the threads and you will be very pleased with this little gem.