DIY Headphones Revisited.

When I first started out in the world of DIY audio, my first project was make a set of headphones. I purchased several different brands of drivers and got around to trying a few of them. I could never make anything work. Well, my Senns are starting to cut out on the right side. I know by looking at the case of these cheap Senns, that I will not be able to take them apart and fix the lead to driver without destroying them. I am very bummed.

 I still have all of the old drivers and I have a cheap pair of shooting ear covers. My problems come when I try to mate the two. I have tried all sorts of methods and dampening but the KOSS drivers I am using just don't respond in a good way. When I just put the raw drivers up my ears with no backing or iso, they sound OK if not a tad bit fat in the middle. Once I have them temp mounted, I always end up with way too much mid range and they sound honky and terrible.  I just can't get anywhere near even the sound of the raw drivers. Compared to the Senns, they are laughable. I am talking about the cheap-O Senns as it is. eH150. Not even a good set like the HD555 or other more expensive versions.

I am beginning to think that the shooting covers may be a good source for the band but the ear-cups are just not going to work.

My plans for future testing include.

Using some 2" PVC end caps for the cup.
My thinking currently is I have to move the face of the driver away from my ear. Dampening is only going to reduce high end and fatten the bottom. I need to attenuate the mid range down a lot according to my EQ, which I leave flat for the Senns.

Is this the correct thought process?
Hopefully, once I get a good idea of what to do, I can try to find a set of those SFI 120z Ortho drivers to fool around with. I will, one day, have a pair of headphones that sounds great and can stand up to the abuse I put them through.
 Any kind of insight is appreciated.