So I've drove the Baja 5t on castle xl2 setup, would like to have som more juice

If the 45c lipos are of larger size and not to old ore well used it should be sufficient. with an larger motor\lower kv motor and higher voltage it doesen automatically mean it will draw an higher current, often the other way around. but it depend on the gearing.

With the MGM esc you also have to use an external bec ore as i did an small life receiver pack.

this is mine with mgm esc and castle motor on 8s.
http://www.youtube.com/watch?v=20f_CkN4bcc

[gizzmo79]

Okey but what do you men by larger size? 5000 mha or more?
I'll think it would be the easiest to use an external bec.