Trying to think of another big German WW1 gun that is similar to the British 6" Gun, and I hit upon this one (the German 21cm Howitzer is similar to the British 8" Howitzer). I'm thinking that a certain someone may want to make a kit to equip the Germans as well as the British are equipped.

15cm Kanone m16 on Landships

The page, linked to above, includes detailed scaled plans as well as many photos such as this one:

Dear PDA,

this gun is also a candidate.
Best regards,

Strelets

Another good choice this gun was also used in WW2 with it seems no real visible alteration, though quite a few photos show new pressed steel style wheels with solid rubber block tyres...

Cheers

That's good news Strelets.

Maybe this one could have a late war crew, and the 21cm Mörser could have an early war crew?

Or separate crews?