Micro Enginnering bridge instructions

[Sumpter250]

I thought this thread was dead.

Which is why I responded, it was three days without response.

This kit has very brittle plastic. Many of the parts are busting, even before I snip them off the tree. The only gluing I've done so far is put pieces back together

This surprises me! I didn't see this problem when I built mine, and have not seen it appear, as the model ages.
When you said "add on", I remembered that those were available, and that I didn't get an "add on kit". I suspect that I had the basic kit, there were only four bents (OK, two towers), which I split into eight bents.
I did find a picture of the 320' kit. The 80' sections, three I believe, are deeper than the 40', but should have the same "pieces", ie. girders, vertical braces, and horizontal braces, which should assemble the same way as the shorter spans.
Is it just the braces that are breaking, or are the girders also breaking?
The company was founded in 1964, so I don't know if this address is still valid, but it's worth a chance. The company is still in business.
Micro Engineering Company
1120 Eagle Rd.
Fenton Mo. 63026
You might be able to get an instruction sheet directly from them, and they might be able to help you with the brittle parts.