I am planning on ordering some smaller gas jet screws for my 17, since I have begun shooting it suppressed.  I'm sure most of you realize this, but I just noticed when cleaning the other day, that the two gas ports on the plug are identical.  I had assumed that the SCAR was similar to other rifles I've had where the plug has a smaller port for the suppressed setting.  What the suppressed setting does is vent the pair of smaller holes in the top of the plug, reducing port pressure that way.  I was wondering if, in addition to, or instead of, messing with the gas jet insert, the system could be tuned for suppressed use by enlarging those vent holes?  Any thoughts?

I would leave the reduction ports alone and just utilize the gas jet screws. If you want to conduct testing out of extra free time then order a spare regulator to test on. You are more and likely though going to have to utilize a different gas jet screw in conjunction with your reduction port resizing to find a sweet spot. In which case why have bothered with opening the reduction ports. You have to account that the performance of the gas jet screws is dependent upon the size of the reduction ports and that total performance is dependent upon your particular suppressor and ammunition.

TL/DR: Do not mess with the gas regulator ports. Buy the 1.30 -1.40 screws and see what your gun likes. Most find their sweet spot utilizing the 1.30 or 1.35, I myself utilize 1.40.

I think you are probably right.  I intend to find the optimal gas jet screws for unsuppressed function first.  Then I might buy an extra gas plug to mess with the bleed-off ports if I think that suppressed function could be further improved.

The sizes in the regulator are the same size but when rotated it vents gas out instead of into the piston.