Improving performance of RealTraps Mondo Bass Trap


I was originally going to purchase GIK Softfit Bass Traps because they had much better performance data compared to the RealTraps Mondo bass traps installed across a corner. However I was able to pick up some Mondo bass traps at a very good price. While I am pleased with the results of the Mondo panels I am wondering if I can improve their performance by filling the space behind the panel with some material. Would this improve the bass trapping performance? If so, what material is suggested?

Thank you.
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If budget is a concern you might look at these Cornerblox. Reasonably priced and should fit behind your traps. I ordered a set and delivery was prompt.
Thank you Timrhu. I just wish they publish some data. I'm trying the get better performance from 60hz and below.
I use a couple of Real Trap products (a Corner Mondo trap on a stand, and a Corner triangle trap underneath it on the floor). In that part of the room, I have no sound issues at all. Call real Traps at 866-732-5872. Jim was very helpful to me in selecting acoustic treatments for my listening room.
They do have this on their web site. Although the lowest test frequency on the chart is 125Hz, the data does look pretty good for the price.

I attached some extra Auralex pieces to the front of mine for an extra couple inches of foam. From what I can tell the foam is identical to the Auralex foam. Both companies are located on the north of Indianapolis. It's obvious that the Cornerblox are cut from a 12x12 inch square piece. I'm thinking of asking if I can get an 8 foot long 12x12 inch square piece to stick in the corner.

I have no affiliation with this company, just use their stuff.