The only reason they did the ports that way is to reduce port noise and help its overall efficiency. If you want to make them shorter, then just do one 4" port. But the two would sound better. Only thing I would have done differently is either braced the endcaps or make them thicker. I would run maybe 3 or 4 all-threads across with t-nuts at one end and bolts at the other to hold the endcaps on better, but thats not really necessary. Either way you do it, its most likely going to sound great.