What belt for eps conversion

[neil a]

What belt is required when doing the eps conversion , using the cup alt set up.
I remember it has to be one ply less to avoid rubbing on the plastic cover.

 

[Fraser.J.]

5pk847 long

 

[bloke]

838, longer always seem to slip a lot of the time.

 

[R29TJR]

5pk847 is what I plan on running and I also think @GrahamS runs this length also.