Well, like me you can consider yourself very lucky to see one Gary, Thomas Fox didn't convert very many at all- barely into double figures, cost an absolute fortune and needless to say involved a lot of work- altering the key guides right through the door slabs to fit the Mersey keys vee-bits, all new glass plates to match plus re-wiring all the relockers etc. Plus they had all the micro-switches and additional electronics which was unheard of on G1A's back then.

Have to say hat off to you for making your Mersey tools extended extra long- now that's real forward thinking at work!
99.99% of them, and that must be many hundreds of thousands, are on very thin doors and filing cabinet styles- which is of course what they were designed for. Even with glass plate protection the doors barely total more than an inch or so thickness, which is why Mersey keys are so short.
Sounds like you got it sorted though if you ever see another on a G1A!