I have a bunch of engines and a digital scale so I weigh them. In ozs , OS 46 16, OS 50 18, OS 91 surpass 22, Mag 52 2stroke 18, YS 63 18, Saito 91 19.

Fuel consumption at full throttle is about 1 oz per min per cubic inch for 15% nitro. If you burn 30% nitro power goes up about 10% and fuel consumption goes up more, like 30%.

Most 4-stroke engines produce about 1.1 lbs thrust per cubic inch (YS are good for about 1.3) Most 2 strokes are good for 1.2 lbs thrust per cubic inch. The OS 55 probably isn't magic - it will probably produce 1 lb more thrust than the 46. It probably won't like 30% nitro.

You have a 5.5 lb plane, same as my Mojo 60. A Saito 91 flies it nicely, some run Saito 1.25's on the plane. I am not a huge power guy but I don't see a OS 55 on my 5.5 lb 3d plane. I have flown 4 lb 3d planes with an OS 46 and unless my wife loses her job I won't do that in the future. I have a Mojo 40 (4 lbs) with an OS 50 on it and it is just OK. I have another 4 lb plane with a YS 63 on it and like that fine.

I fly with a guy that has a 50x and a Saito 82. Unfortunately he is still fiddling and won't get it flying very soon. It should be ok but not spectacular.