DRG, I went and looked in Panzer Tracts
Pz.Sfl Ic (5cm Pak 38 auf Pz.Kpfw.II Sonderfahrgestell 901), there's no hard dimensions on it; the cannon was a modified Pak 38 with the breech and mount adapted from a 5 cm KWK gun.
No hard data on ammunition stowage #s; the dimensions given in
https://tanks-encyclopedia.com/ww2-g...panzer-sfl-ic/
Dimensions (L-W-H, based on VK 9.03) 4.24 m x 2.39 m x 2.05 m
Are probably good enough.
But while researching this in Panzer Tracts, I found ANOTHER ONE.
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Pz.Sfl Ia (5cm PaK 38 auf gp.Mun.Schlepper)
On 5 July 1940, Wa Pruef was authorized to develop a light Panzerjager for the Luftlandetruppen (Airborne troops). The design chosen was a 5 cm Pak 38 L60 mounted in an armored superstructure on a converted VK 3.02 munitions schlepper chassis designed by Borward.
To save weight, the forward gunshield was to be composed of Schottenpanzer (spaced armor)
2 x 4mm plates (front)
2 x 3mm plates (side)
Frontal/Side Armor was to defeat 7.92mm Steel Core AP bullets.
Mass was 4500 kg, top speed was 30 km/hr.
Crew was 3
Panzerprogramm 41 called for 3,144 of them to be built; but production wasn't scheduled to begin until 1943.
Two trial units were built by 1 July 1942 and sent to the front for troop trials. On 8 Aug 1942, 19 PzDiv reported the serial numbers of the two units back to OKH.
Unfortunately, the experience report from Panzerjager Abteilung 19 on this was lost to history -- we know it was sent to OKH on 18 Sep 1942, but a copy of the report wasn't included/retained in 19 PzDiv's war diary.
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Also, this rabbit hole was worth it for me as a researcher, because I found out about Panzerprogramm 41; something I did not know about before.