window coil balances

I need two coil blances probably of 152 series. No weight written on the spring except an F.

The marking F could be a 7 on the reverse side. Based on the color (brownish) I think it was a 152-7.

My window lower sash weight is 14.5-15 lbs. Should I use coil balance 152-7 or 152-8?

The old 152-7 were broken. So I am thinking to use 152-8 which may be stronger and still in the upper range. Usually you recommend rounding up after sash weight is divided by 2 so 152-8 would be the correct part based on that calculation.

What are the part numbers for the upper support for 152-7 or 152-8?

Thanks a lot.