Sealing ported enclosure to reduce boom

Hey Ifsixwasnin9, put a sock in it.
Seriously, I owned a pair of Acoustic Energy speakers that came with port plugs. The speakers had more bass than was needed in my small room. With the plugs inserted the bass was much tighter and tuneful. Give it a try.
Nice screen name BTW.

I agree with stuffing the ports too. You may want to position them differently (more or less toe-in - closer or farther from front or side walls - etc).
If what you are asking about adding 'fill' as in adding sand or shot to them that will tighten the sound from top to bottom. Try one thing at a time. Adding 'fill' may also make them forward sounding .
That's my opinion and good luck

Partially blocking ports is a valid option. You have to try it and see.

Yes, I have in fact even used socks on occasion to do it.

I had a serious boom problem that was practically eliminated by repositioning the speakers. Sometimes, the problem is the room.
Try the following experiment: if your room dimensions are x by y, put the speakers at 1/4 x and 1/4 y from the respective walls. You might not like what they sound like there--they may sound a bit thinner than what you are used to--but what you are after here is to see if the boom goes away.
If it does, then your primary source of boom is probably room-related. It's a pain in the posterior to deal with, but the laws of physics are not mere suggestions...

Go to the Cardas site and use their room placement guide. Helped my speakers and cost nothing except the effort to move the speakers.