If it's only visible in model viewer then it's okay. One "invisible" window shouldn't cause performance issues.

I like how you removed the lights and sirens from the civilian version, and also the windows that used to appear on the undercarriage. The civilian van must have been an afterthought since it seems to use the same model as the ambulance, and there is a window texture that appears on the underside of it which can be seen in the model viewer.

One last request for this addon, could you please also make this also available as a 'Personal Car' so that it can be distributed to citizens? I believe citizens with large enough families in the USSR could purchase them if they had enough kids to warrant it, so it is somewhat historically accurate.

You're welcome :D

Thank you so much, this turned out beautifully!