I tend to use these to make trusses for solar panels etc. Would it be possible to extend these to length 8 just like on tanks? In the spirit of count reduction.

Not possible without creating more models, and all of the headache and extra work that entails.

Feel free to use the model-definition system to create double-length segments using the SUBMODEL setup.

Edit: After the big update is done, I'll see what I can do to create the additional lengths. For now though, it is too much work for me to commit to in the foreseeable future.

No problem. It's just a nice-to-have and I thought I would just throw it out there.