dividing single slot port into 2

the thing is i really want my sub central in cab not to keen on sub one end port other,i understand that port width maybe to small 1.5 inch each side so you say shrink height of cab to get better width port each side is that correct.if i shrink height then i lose more cft.
so what i wrote below is that correct if i want split port into 2
3.4 cft internal. the port height is 419mm that will stay the same the width of port is 88mm that will half to 44mm length to stay at 20.i was given formula to work out width of port. cuft of box after displacement x 16 = sq in of port opening then dividing this by internal height gives me the port width.recomended lengh for dd tuning was 20 inches gives between 35-40 hz.

so my way of thinking is 88mm x 419mm / 508mm long
eg 44mm x 419 /508 long x2

 

i think i might have it,
eg 3.4 cft using 2x 4inch round ports by 10 inches long all i did was find out how much surface area each port is then convert that figure into slot port. is that the correct way. yes i know its not the correct port lengh just example.does this sound or look right.