NH 648 mininum belt length

Hi everyone, long time reader here but this is my first post...

 

I've searched but can't  find a minimum length for the belts on my NH 648 roller.

 

I have them all off now and plan to cut about 1" off both ends and make sure all the belts are the same length and fresh clips & cable..

 

Book shows 343" for a length but nothing on how much ( if any ) shorter they can be if all the same ??

 

Thanks

NH 648 mininum belt length