Square is fine.
I've seen no difference in accuracy or performance due to patch shape.
Just make sure your patch material is thick enough to provide a good seal and to hold enough patch lube.
For that .72 I'd want something in the .025" thick neighborhood.

A few years ago a fellow member here suggested I try some good cotton denim material from my local fabric store.
I got a range of thicknesses from about .018 to .032 and I've since been set up nicely for anything that comes along.
The denim fabric pieces I got are different colors too, which has been helpful in segregating for one rifle it the other.
I carry it in strips cut to appropriate width, then I cut to length as I set the ball.
Works great.

Cheers
Tinker