Hello first post on the forum (I shall have to introduce myself at some point!).
Also Interested to see how this progresses. I am doing a similar conversion at the moment and my package of Penbits bits are in the post (to add to the various Brassmasters and Shawplan/EE parts I have stockpiled). Pete Johnson was kind enough to exchange a few emails on this topic with me last year and I have just ordered a back issue of the relevant RE with his article in it.
I am using a model from my modelling youth that spent the best part of 25 years in a box and it is very much something I'm pursuing out of nostalgia (as well as it being a nice little modelling project).
You have given me pause for thought around some further additions to the bottom of cab front that I need to make. Perusing David Clarke's Class 24/25 book last night also indicated that there is more to the lower body sides than a casual glance would suggest.
One area I am in the process of tackling are the mods to the roof panels and various exhaust ports. I have made a start on this and have fitted Brian Hanson's rather nice replacement fan grille but still have quite a bit to do elsewhere. I would be interested in seeing some better reference photographs (I have been relying on Brian Daniel's site and only have my own photos of a different Cl. 25 variant to the one I’m modelling taken while at Grosmont last year). So I’d be interested in seeing how you tackle that.