is this possible? enclosure design

Both of these enclosures are 6ft^3/ sub I need a enclosure design that would hold 2-12" solo x's... Here's the catch.... I would like the to be able to make the ports interchangeable... 1 for daily and one for comp.. "SPL is the largest and most efficient enclosure design. The SPL delivers the sonic output needed to win SPL contests and it produces bass notes in a “Livin’ Loud” manner. This design is intended for test tones above 68/56Hz; playing music with frequencies below 68Hz will result in subwoofer damage." VentedSPL (MaximumEnclosureVolume) 6 ft3 (170L) + port displacement, Fb=68Hz Port: 250 in2 (1613cm2) area x 9” (22.9cm) long Power Handling = 2500W Peak above 68Hz Model: S12X VentedSUV (TheOneToDo) 6 ft3 (170L) + port displacement, Fb=45Hz Port: 60 in2 (387cm2) area x 6” (15.2cm) long Power Handling = 2000W Peak Is this possible?

Work out the tuning freqs so that both ports are the same length.  Then, you make a smaller sq in MDF insert and slide it into the larger port opening when you want to change Fb for daily.  You can work out construction details.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.