D.I.Y. Bass Traps- calling acoustic techs....

I have been reading about diy bass traps but still have some questions. For me I am going to build some round tubes with fiberglass pipe wrap or Rock Wool. This is avail locally in 3 ft sections and 12 in diameter with a 2 in thick wall. The paper cover can be removed and wrapped with cloth. The ends can be glued on with mdf or plywood.
The problem I have is a 50 hz bummp. Most of what I am reading says these traps are good around 100 hz. Do you think stuffing each tube with more fiberglas insulation will make them more effective?
If so, should it be packed loose or tight?
To deal with a 50 Hz bump you will need the trap to be VERY large in diameter. This is an absorbing kind of trap and to be effective needs to make it to the 1/4 wavelength, that is roughly 5.5 feet.

If you go to our resource page. you will find there is an article on bass traps by Ethan Winer which we supported. This is a good intro into types of traps and how they can be effectively used.
FWIW - large = minimum of 16 inch thickness for absorbers ...and probably all four corners treated extensively (floor to ceiling)

You could use resonators but they tend to ring - and in the end it may be better to have a hump and a better RT60 than no hump and a poor RT60.
The biggest problem in my room is a +5.5Hz bump at ~100Hz. To reduce it I'm going to try adding a set of the pipe wrap bass traps.

Jon Gale, who is usually credited with this DIY plan, wrote on one forum that there is a "supertrap" version. The biggest change is the addition of a second smaller fiberglass tube inside of the first one. While a little more complex to build they are supposed to be more efficient (more absorption in a smaller volume).

Can anyone offer details about the size of the second tube? Is there a specific ratio between diameters involved for optimum efficiency or tuning?
Did something similar with stacked 20" pipe insulation and rock wool. It's an expensive way to go and not very effective below 80Hz, no matter how it's stuffed. For 50Hz, you have to get real creative, like built-in, floor to ceiling membrane traps. 50Hz problems are not that typical and may be just a harmonic or resonance (pushing back) from an adjacent room.