Hardtail frame size
 

Hi. I'm want to get a oppinion for a hardtail frame size.
I'm 168cm and have a inseam of 78cm.

What frame size would fix better for me ?
A 17'' or a 18'' ?

From the formula 78 X 0.226 inseam results a 17.6 frame. Now i ride a 19'' frame, but is a little big to me. On long rides a have a little shoulder pain cause it's stretching me a bit.

Should i go 17 or 18 ?
My ride style in not agressive, want to go with more confort, so that i will have no pain on longer rides.