Depending on the site one views... Perhaps 24 of these were built in late 1944 / early 1945, and maybe 6 "hetzer" hulls were converted for 6 additional units. There seems to be no readily-accessed info as to whether any ever saw action.
I have never seen any "in action" pics - and actually none which show anything other than what appears to be a straight one-color paint-scheme (dunkelgelb base coat). But we can dream!
The 15cm s.IG. 33/ howitzer was successfully mounted on other 38(t) - derived chassis and proved mobile and to not over-burden the chassis or its suspension (but the ammo was quite heavy at 82 lbs per projectile, which effectively limited the number of rounds that could be carried) - the Grill 38(t) H and M both being successful self-propelled arty.
Existing "factory" pictures show that the hull and chassis sat pretty level on its suspension and that this vehicle was not noticeably "nose-heavy", unlike the Jagdpanzer IV - "Guderian's duck".
Image borrowed from a public web-site and posted HERE for discussion purposed only.
Cheers!
Bob
PS: I really look forward to at least seeing this kit get built by someone, if not getting one myself! It's VERY cool to see someone bring this out in 1/35 styrene, and I'm pretty sure that Dragon COULD do a good job - they have a good s.IG. 33 and vehicle mount kit available, and they have good 38(t) running gear and bits- and even tracks of the pre-cut-and-cleaned "magic Track" sort (though these may have used a different track set than the Grille M and Marder III vehicles did...). It could be something really good! Hope springs eternal, even when we are talking about the notorious Dragon.