Questions bore reducers, lipos, and motor mount, e-revo

Hello i just had some questions that i cant find in a direct format, i have spent more hours on this site than i like to admit

this is all for a conversion e-revo, and of course i will be getting the mmm
i will at first use my hv6.5 though(i want to wait for the esc motor combo on the mmm). my question is when using the bore reducer from this site, will i have a much higher chance of snapping the shaft on the motor (hv6.5)?

for lipos 5s1p or 5s2p the 5s1p is a 5000 mah and the 5s2p also totals 5000mah is one "better." I do understand the series and parallel concepts of increasing voltage(s) or capacity(p)



next with the rc-monster vs the tekno motor mount. is one for using the clutch bell instead of spur (tekno) and the other is for a direct spur (Rc-monster)? i think i have it right or can one do both. and in the same breath what is the difference in action of either.

thanks for your time
j