Thanks Phil
One thing with the original ports, is that they're 2.75" I.D. at the outside but as they dive into the cab, they taper to 2.25"
They may have been fine for the OEM drivers but i'm wondering if they should be bigger, so i've ordered a pair of 100mm ports from CPC , and they're 114mm long.
Roughly, ( very roughly ) the combo is 2.47ft Cube, or 0.07M cube. If that equates to about 70 litres, then the Beymas should be fine as they need 30 litres each. Of course the back of the drivers use up some litreage, so it wont be quite 70 litres