RE: Four stroke muffler and cowl
I feel your pain! It's a big bummer to cut holes in a beautiful cowl. At least 4-stroke mufflers are usually smaller than 2-stroke. In addition to your stated options, you can investigate other exhaust pipes/headers and mufflers to try to direct the exhaust to the most desireable exit point (like at the bottom of the cowl). Many manufacturers make flexible pipes and small in-cowl mufflers. You'll just have to search around on sites like Tower Hobbies or Horizon Hobbies. Good luck!