I missed the discussion.... I must admit I only visit concertina.net occasionally.
The action in this particular instrument was the Wheatstone hook type, which is even worse than Lachenal's. Instruments I decide to rebuild have either a lot of potential or are completely destroyed. The goal is to make the instrument as good as possible. Something I would want to play myself. This quite often means replacement of the action because:1 it has a hook type action, or (part of the) action is worn and makes accurate pressure adjustment impossible. This is quite common in heavily played Wheatstones.
(I just read part of the discussion and noticed Goran calling it the "Geuns" action.....True, we also use this action in the Geuns-Wakker concertinas, but Harry has nothing to do with concertinas or the Concertina Connection.... He is an independent Bandonion maker, in my opinion one of the best. His concertina activities are limited to our G-W line (joint venture).
There are other parts that we 'improve' ( at least we think so), like a different design bellows with a higher quality leather (compared to post 1920 instruments). In standard design concertina bellows tension (when the bellows start to 'pull back' when pulled out) build up starts at about 50% of the maximum bellows travel, usually with a very steep curve. In our design this is point is moved up to ca. 80% of the maximum travel (80% tension free bellows travel).
Key pressure is set at 60-70 grams. To my knowledge Wheatstone and Lachenal never measured/adjusted their key pressure. Finally I use specially developed software to adjust the reed performance (harmonics, amplitude). We use 3 different 'valve weights' for every valve size to fine tune reed harmonics and amplitude.
I expect certain people not to agree with our philosophy.... but as a musician I am interested in the maximum musical performance of an instrument. This is done with every musical instrument used by professional musicians, e.g. most Steinways and Bosendorfer grands have replacement Renner actions...
So there we have in Wim's own words a statement of the sort of personal design principles we only wish we had from Wheatstone, Lachenal, and the rest. Valuable information, in my opinion.