I was told by more than one dealer that the TT is measured from the back bumper to the tip of the hitch triangle so you buy a 30 ft trailer and really you live in 25 or 26 ft of it. With a Fiver, the length is from back bumper to the front of the fiver so it is all liveable space that is counted. When buying one must be careful to know that are when buying a TT they will think they are getting more livable space that they are not.
Chevy Silverado 2500HD with Duramax engine and Allison transmission
2002 Sunnybrook 34BWTS with lots of goodies
Pullrite Superglide Hitch, Prodigy brake controller
S and S Co-Travelers and along for the ride is Ketzel the wonder cat.
Trailer overall length counts, but tongue does not count for lighting.
OP is adding intermediates lights for safety.
Lighting when manufactured or for first retail sale must meet the Federal Chart previously linked. After that point -the home state regulations override the Federal statues.
Washington has it's own performance standard for lighting and placement. Many pages of Revised Code of Washington, RCW, to research for Washington residents.
In Washington -home built trailers are easy to license -that is if you can account by receipt for all parts and components. Problems arise when trailers are re-purposed from scrap without title or salvage documentation.