When is an Ultra Light not and Can it be a LSA

[martymayes]

or buy the kit with anything I want that exceeds the ultralight rules, build it and then register it as an E-AB.

If you go that route you can operate the aircraft as an LSA.

[Dana]

Thanks Dana. So as I expected, if any mods to the Aerolite 103 result in exceeding Part 103 limits, it is no longer an ultralight by the rules, would fit the LSA definition but according to the FAA, basically can’t be registered in any “useful” LSA category.

Leaves me with two alternatives, keep any mods to an existing ultralight within Part 103 rules or buy the kit with anything I want that exceeds the ultralight rules, build it and then register it as an E-AB.

Correct... with the caveat that the kit must leave enough for you to do that it meets the so-called "51%" rule.