Having gleaned an idea of the optimal layout for the elevation and recoil units, it's time now to make a support bracket for the elevation unit. The recoil unit, of course, is a good tight fit on the gun tube. Screws from either side of the recoil/breech housing (in the holes formerly occupied by the original trunnions) will apply extra grip.
Louis (Imcq11) observed lately, in his current Meisterwerk Stuart build, that he relies heavily for his amazing scratch builds, on a good supply of styrene in key (mm) dimensions, and ditto with brass tubing. Well, I follow the same principles in my (it has to be said) more apprentice-like scratch build efforts.

I also rely on scrap styrene. It's amazing what old can be done, as well, with old bits and offcuts of styrene. There's always a use for them- so don't chuck 'em- unless your hobby-hoarding has almost reached the ceiling by now
Here's what I made- in rough- based on current requirements:

The base of the support unit was built up in layers of old styrene. The aim was to get the elevation unit perfectly horizontal, with the front of the unit resting on the floor...yes, it's an awkward shape. Still, the resulting unit does give good stability.
It will be bonded to the turret floor, in the optimal position.
In the photo, below, the recoil and barrel have been linked, and fitted onto the mantlet gun tube. I removed the elevation arm channel, and relocated it so that the amount of travel should correspond to the full length of the channel (2cm).
Now the elevation arm, and unit are in the optimal position, relative to the recoil breech, and elevation arm channel.
Now, a bit more relieving to the roof, and then I'll have to move on to the next challenge: fitting a turret ring. That's not going to be easy either, as the turret is a very loose fit in the aperture of the upper hull.

C'est la Vie, C'est La Guerre
A couple of observations for anyone thinking of making an RC version of the Comet (or Cromwell, for that matter). Make the roof a one-piece fixing (as with the Tamiya Tiger 1)-
It will make life a lot easier. The other one is that it
is possible to fit recoil and elevation units- but it's tricky.

"Get your facts first, and then you can distort them as much as you please"- Mark Twain.