HI there. I am running an HO scale setup, with 18" radius curves, and was wondering what the maximum scaled size of rolling stock I can use without derailments. I have some 40' and 50' and they are fine, but I don't want to buy any bigger yet until I know how big I can safely get. Also, as a side note, I just bought a Broadway Limited Hudson J1e (TH&B) steam engine. Love it!!! Thanks for any information in advance. I posted a long time ago asking for advice on my layout. Unfortunately I had to take it down because my daughter grew up enough to reach the tracks and started pulling it apart on me. I have since moved rooms and starting building my layout up again.