They look great, I will definitely want a number of them.
I have just been looking at Horst Schubert's book on the Hetzer and G13 (Schiffer Military Volume 27 ISBN 0-88740-238-0) and your excellent 3d renderings. According to the description the Hetzer has twelve and six hole idlers, the four hole idler shown as the late production track unit would appear to be a G13.
The book mentions a G13 at the museum in Munster masquerading as a Hetzer.
That is of course from only one source.
[Edit]
Okay, the Osprey NewVanguard lists five different idlers including four hole - the modelling book has a May 1945 model based on the US Aberdeen proving ground with four holes. The Osprey modelling book mentions seven variants but does not list them.
The Czech uprising example in their museum from May 1945 has six holes, that was liberated from the Skoda factory without a gun.
There do appear to be a lot of G13s about:http://the.shadock.free.fr/Surviving_Hetzers_G13.pdf