By experience,GP7 frame will not fit,unless you made some modifications,to make fit the bottom frame to the shell..
for the RS11,I have no idea but it could be possible,need to try to see wath it can be possible or not...
but,if you have Athearn F units bottom frames,it fit very easy with Life-Like F unit shell,the only work to do is in the front coupler,it stick directly on the frame,need to remove it,the,make a bigger hole to fit the bottom frame coupler in..
here's my f units,Athearn frame and Life-Like shell,still have works to do on them,a bit of detailling,renumbering them and converting them to DCC,cause I'm finally do the step to DCC next month..