That 'mesh grille' on the back of my amp is the standard grille that came with the amp when I bought it. (it's the 3channel dual rectifier but not the multiwatt version). I think that the multiwatt dual rectifier has a smaller 'tube guard' right? (as in the picture I found below)
The control switcher is attached to the grille with 2 small tie wraps, so no glue or screws are used. The 4 small cables that you see are George L's that I cut to be the perfect length between the external switching jacks and the control switcher inputs. Again using small tie wraps to hold the 4 cables together. The small size of the control switcher also means that I can still use the Mesa dust cover on the head. And it only adds some minor weight to the amp.
I'm just thinking if you have the multiwatt version how you could attach the control switcher to the back? As you can see in my pic the control switcher is all the way to the right of the amp, near the rectifier tubes. Since I use silicon diode rectification and not tube the 2 rectifier tubes are not used, so they don't warm up and you don't get any heat from the tubes to the switcher. If you would connect the control switcher to your 'tube guard' that might give a heat problem as the 4 power amp tubes do become pretty hot. Maybe you could swap your tube guard for a grille like mine? The grille is only attached to the amp with 4 screws (see picture above) in the 4 corners, so you need to have some wood in the corners to attach the grille.
I've just found this picture... I see that there is 2 small pieces of wood in the left and right corners of the amp, so you probably can use the same grille as I have and just use 4 screws to attach the grille. You might be able to order a spare back grille from Mesa?
What I also did is I bought a 5m standard midi cable, a 5m guitar cable and a 5m power cable and I created 1 big cable using 'cable snakes'. This cable runs from my pedalboard to the back of the amp where the 3 cables come out 1 to the midi on the control switcher, 1 to the input on the amp and 1 to the power adapter to power my pedaltrain. That way I have only 1 cable running from my pedaltrain at the front of the stage to my amp. (I hate to have cables everywhere
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The reason for the musicomlab switcher is that I have a small pedaltrain with a lot of pedals and I didn't want to buy a new pedaltrain, so I did look for the smallest footprint switcher. It fits the pedaltrain 2 nicely and I still had room to fit the other FX pedals. (all cables are George L's to save space on the board)
If you find a solution for your setup please post some pictures as I always like to see other people's solutions for this kind of stuff ;-) .