When should I register in NY?

I am trying to figure out at one point in my consturction I should register my trailer. I am building on a Harbor Freight frame. In New York, registering that is as easy and taking the supplied certificate of origin with the sales receipt (shows tax paid) to DMV. They give me the plates there with a 10 day temporary inspection. I then need to take it to an inspection station (privately run authorized garages) for inspection within 10 days...basically lights, tires, etc. This is a yearly safety inspection and not part of the registration process.
I am trying to decide if I should register and inspect it (since, technically, that needs to be done within 10 days of registration) as soon as I finish the frame, as soon as I finish the (overhanging floor) or wait until I build the whole thing.
I kind of think maybe after I build the floor, which will hang over the frame about 1 foot on each side. That way in case the inspectors have a problem with that, I'll hear about it then, vs. after the thing is done. Since all I am registering is the frame, I don't know of any problems...but I could be missing something in the law. That way I can mount my lights to the floor frame and be road-ready then (since the lights need to be mounted to inspect it). If I mount them on the HF frame, the floor will be wider than the lights, and they are supposed to be "as far apart as pratical"...so I'm thinking I should install the floor first and then mount them to that.
My main concern is if there is something in the law about permament changes (bolted on in my case) to a trailer frame. I don't know of anything and may just be overly worrysome.
I am trying to decide if I should register and inspect it (since, technically, that needs to be done within 10 days of registration) as soon as I finish the frame, as soon as I finish the (overhanging floor) or wait until I build the whole thing.
I kind of think maybe after I build the floor, which will hang over the frame about 1 foot on each side. That way in case the inspectors have a problem with that, I'll hear about it then, vs. after the thing is done. Since all I am registering is the frame, I don't know of any problems...but I could be missing something in the law. That way I can mount my lights to the floor frame and be road-ready then (since the lights need to be mounted to inspect it). If I mount them on the HF frame, the floor will be wider than the lights, and they are supposed to be "as far apart as pratical"...so I'm thinking I should install the floor first and then mount them to that.
My main concern is if there is something in the law about permament changes (bolted on in my case) to a trailer frame. I don't know of anything and may just be overly worrysome.