The 24.7 has been working well so far. Holds a tune, runs well, idles well, broke in pretty painlessly, gobs of power and it seems to be pretty economical as far as fuel goes.
I've only run about 1/2 gallon through it, but after that first quart of breaking in, it's been a blast. 15/36 gearing, 3.3 chassis and standard ratio trans and it still pulls a solid wheelie when it hits second.
I've learned a bit of throttle control. The 21RG wasn't anywhere as punchy as this is. I'm glad I decided to go BB. The 18TM is a good engine, but there is no replacement for displacement...