Replacing pots on 'G'-Classic w/ ground board ...

[classic]

Did someone of you ever replace some pots on a Gibbo with a metal ground plate ???
Wow ... that's not a job being done in 5 minutes as I've expected before ...
Although having had taken all upper nuts and pointers on the top the pots and the ground plate still remained in the cavity like glued at it or fixed otherwise ... as an amateur I didn't risk to pull very strongly avoiding to flaw my beauty ...
So - I had the idea to turn the pots counter-clockwise ... and it was working ... but you can imagine it was a hard job to losen all pots (long shaft) this way ...

The Gibbos had additionally fixed the pots with a hex nut onto the ground plate - from my postion underneath the ground board ... my finger tips are raw now ...
There must be a clue to get it sorted in a smoother way ... does anybody know how to losen the ground plate ???