i think some of the top .21's would keep up just fine, yes.. ive never seen the LRP in action, but usually any sport .28 is about the same or LESS powerful than the .21's... the .21's usually have a more refine powerband..
If i were you, i would look into the go tech motors, i have the .21 5 port and i really like it so far, excellent buy!! they also have a .21 3port sport model for really cheap, just get a dynamite 086 pipe and maybe change the head button from a standard glowplug type to turbo plug type for like an extra $15 and you have one hell of a motor for around $140