if you want the cheapest option cut each flange between the ports, ideally wants cutting on the outside face but it would be very awkward so I it on the head side and it worked still, don't go right through though as it will all twist out of shape if you do.

the thinner you can make that flange between each port the easier it will pull into shape and hopefully not break a stud off in the process.

I had mine skimmed twice, it wartped again after use so I had it skimmed again andcut the slots and it was fine after that.