4 hole pistons

[lovechild]

Just looking at Jorns set up from saturday and noticed hes using 4 hole 1.3 mm pistons, with 650wt durango oil at the front. What oil roughly will that translate to with 6 hole 1.2 mm pistons? is it simply a direct comparison? ie 1.3 x pi x 4 vs 1.2 x 6 x pi? if so for an equivalent 1.2mm 6 hole piston, I would need an oil far in excess of 650 wt correct? or not?

Thanks