The B44 chassis is different from the B44.1 as you can see in this picture.
http://www.rctech.net/forum/attachme...ad-chassis.jpg
So maybe it just wont fit!
You could try turning the servoposts round (I know that 's actually wrong btw), and fitting the servo then, It should be a few mm back that way.
But the best thing to do is probably file the casing down a bit, or file (mill) the servoposts a little thinner on the front.