Frisko,
what is the all up weight of the Majestic 1400?
Based on my limited experience with some of the small planes (OK model planes) OS 46 w/ stock muffler was not enough beside the ugliness.
So far, Oxalys 50 looks larger than the Majestic. If the 46 is just enough to fly Majestic, you may want to use tuned pipe.
The test setup of production version of Oxalys 50 weighed 2500 grams (5 pounds 4 oz) dry. That is with 4 of 9252, 1x 9001, 136HP receiver, NR-4RB battery pack, OS 70 Ultimate. Yes, the Oxalys 50 was designed around YS 63, but test model used OS because of weight.
I am going to build one with YS 63 (electric setup costs way too much).

Ihncheol Park
P & A Hobbies