There are a lot of 4-4-0 and 0-4-4 tanks involved in push pull working, the LMS, LNER and SR all used 0-4-4s for this work. There will shortly be an SR M7 0-4-4 in N (Dapol, using part of the mechanism from their 0-4-2T 14xx). How does the M7 compare in size to the LMS and LNER engines? Just wondering if it might be an idea to suggest using the chassis for a conversion but all my reference books are currently (and for a fair while yet) in storage.
Mike