I thought about doing that but, my Bosch 7 1/4's only cut to a 2 3/8 inch depth. Without making additional modifications to the 7 1/4, it seems that putting an 8 1/4" blade on it would only get me to 2 7/8". (The Makita's claim to get a full 2 1/2" for the 7 1/4 saw and 3" for the 8 1/4" saw.)
is your bosch a wormdrive? If so, go for gold and get the BigFoot attachment (around $200 will turn your 7.25 into 10.25)
http://www.bigfootsaws.com/