could i wire 2 3 cell 2100 lipos in parallel to make 6300 in the sv27 or would i have any problems with run time or any different problems

You may do that but it won't be the same as running 4s LiPo which is the norm.

Ryan

sure u can, just prop up a little bigger and u'll still get decent speeds out of it

2 x 3S 2100mah parallel = 11.1V 4200mah, not 6300mah.
I'd consider using a Low Voltage Cutoff if you are trying this, bigger prop can alter the amp usage...and it won't be super fast, but it'll work.
Make sure you don't connect the 2 3s packs in series by mistake...it'll blow the ESC and likely the motor too...don't ask me how I know.