Register your aircraft for an N-number and get the white registration certificate back in the mail. To do this you need form 8050-1 and form 8050-88. Form 8050-1 is the form in triplicate with carbons so it isn't downloadable. Form 8050-1 can only be had at an FAA office or from a DAR. Fill out the forms and send them to the aircraft registry branch with $5.00. When you get your white registration card back in the mail you may proceed.
Link on the Experimental Exhibition program letter and fill that out. You will need the events you plan to go to, and any airports you plan to fly to for maintenance or proficiency. Use the sample program letter to help. You will also need to fill out an 8130-6d application for airworthiness Under Section II, check 4 Experimental and then 3 Exhibition.
Next prepare your aircraft and logbooks for the inspector. Make sure you have maintenance records for both engine and airframe. And it would be best if you can find and A&P to sign off a current annual condition inspection. Make sure you have a weight and loading form. The inspector will ask to see it.
Call your nearest Flight Standards District
Office and tell them you have an aircraft that didn't make the Experimental
Light Sport Aircraft deadline and that you would like to certify it in
Experimental Exhibition Group IV. That you would like to send
them your Form 8130-6 Application for Airworthiness, program letter
and registration certificate for their examination and after they look over
your package tell them you would like to schedule a time for an
inspection. Be nice and don't get frustrated if the first time they
laugh. Tell them you are serious and that you have all the required
documentation and understand the restrictions involved.
Listen there are hundreds of aircraft flying in this category of
experimental aircraft. The category was designed for aircraft that
couldn't get flown any other way so you may use it too. If they want
more information just ask what it is they want and try and supply it.
Remember I can always help answer any questions and if I don't know the
answer I do know where to find it.
If they say they don't have time suggest that you can bring the aircraft to them on a trailer. That it isn't a very complex aircraft and the inspection shouldn't take very much time. Again stress you have all the paperwork and logbooks ready for them.
Finally when the inspector looks at your
aircraft be ready to answer any questions and/or fix and change anything he
might not like. Such as bolts that don't go through the nut at least
one thread,etc. Bring or have lots of different size tie wraps.
He may want you to secure wires or other things. Have a good set of
pictures with front, side and rear view for him. Don't
just take digital pictures and print them on typing paper, they should be
nice 8x10 glossy prints.
Hopefully at some point the inspector will be satisfied and hand over a pink airworthiness certificate and set of operating limitations. Make sure he goes over them with you so you totally and completly understand them as they are what governs what, where, when and how you can fly your newly certified aircraft.
Good Luck.