Got the two hull parts joined together. They are slightly different heights so I lined up the top of turret rings and I'll make up the difference with plasticard (the HL hull is a little shorter). Cut out the engine deck so I can swap it with the Mato one.
And the postman dropped these off.
I wasn't sure about getting these but I'm so glad I did.
The Firefly Hybrid was made with a M4 Hull (welded) with the front off the M4a1 (cast). Looking at this diagram I noticed that the Henglong M4a3 hull (Late 47) is slopped more at the back*. So thats for the chop (wish I'd spotted this before I stuck them together.)
After much googleing I've found that the M4 rear slopes at 10 degrees to the vertical and the M4a3 can be 10 or 22 degrees. The HL model is 20 degrees so look like it's chopping time.