So... a few test prints later...

Well, maybe more than a "few"...
I ended up with this...

Close to perfect, altho I might redo some parts with a resin printer...

The whole 3-piece cover/fenders combo is seven pieces in total. You could probably do it "as one" if you used a resin printer, but I kinda want to make the whole set accessible to people with lower-end printers. The way I laid out the pieces for printing makes for the best details even with an FDM printer, altho I did uses a 0.06mm setting on some of them. The bolts at the top I decided to do as seperate pieces knocked out of a sheet of styrene.

It fits pretty well, and I am going to include a few templates for cutting and drilling when I upload the 3D files. Also thinking about making a set for a Sherman as well since I have most of the work done. Don't get me wrong, don't want to steal anyone's income with their Shapeways versions. I just think it's nice to have options.

The inside of the sponson has changed a bit since the previous version. Made it a tad shorter so it can slide in from the back. Added a piece to attach the gunner's scope. Might still redesign the mantlet to accept a bracket for the BB unit.

As you can see, there is room for the BB unit (if you do a 17-pounder Firefly move and tilt is about 45 degrees...) and it can even still traverse, raise and lower for an acceptible amount. Loading the BBs... not that's a bit of a puzzle to solve. Also made the bullet-splashguards which came out very nice even with an FDM printer.
The new turret I bought the file for online worked out great when enlarged from 1/100 to 1/16 scale. After a test print at prototype-speed (0.3mm layers in about 6 hours) that came out quite good and satisfactory scale- and detailwise I decided to go for a production print at 0.08mm layers.
Cura said it was a 24 hour print. Started it around 8 in the evening and checked in every now and then. Went to bed. Got woken up around 7 the next morning by SWMBO that she had woken with the power off... a circuit-breaker had tripped! Found the cause of the trip (gawddamn xmas lights...) and managed to restart the print. Thank the Great Sherman In The Sky for 3D-printers with resume functionality....

After some sanding and some added cast texture with Milliput on several pieces it should look awesome under paint.
To Be Continued...
TTFN,
Rob