Some of these are fuselage and some finishing kit. It is all a blur.
1. I went with all the parts one could buy from Aircraft Specialty--I think that $39 for the U-1024 is a real deal.
2. Locking push-pull lines for the air vents--this is critical to keep heat out of the cabin in the summer--or so I have read from Tim Olson
3. Replace plastic air vents with aluminum (already stated), but well worth it.
4. Replace all pass thru with the ones from Aircraft spruce (
https://www.aircraftspruce.com/catalog/hapages/ssfirewallkit12-04762.php). The one from vans are sharp and there needs to be one extra one. I put all wires thru a main central pass thru and the push pull controls through the stock pass thrus. I am concerned that the cables might need to be replaced at some point.
4. I have stock main wheels and a Berringer front wheel. The stock wheel will not allow one to put on the air cap--maybe van's changed that. I would consider all wheels Berringer.
5. I have not done this, but I still might. Change out the door latch for the one from JD Air.
https://www.jdair.com/handles-latches/ This would have been much easier to do when assembling than after the fact.
6. Skybolt fasteners along the top cowl/FW intersection. Maybe piano hinges are fine, but these are very nice. If I were building again, I would put along the FW/bottom cowl intersection.
7. If you go with the Tosten grips, do it when you order. I have an extra pair of sticks in the garage.
8. I punted on the routing of the stick wiring per the plans. I put the wires to the sticks throughs the bulkheads and out a lighting hole.
9. Install the rudder control from Aerosport (
https://www.aerosportproducts.com/product/rudder-trim/)
10. make sure the coax cable supplied with the empennage kit is long enough for the transponder antenna (you probably won't know until the fuselage kit is done). Mine was too short. I had to order more coax any any, so I cut that one up for other uses. Or put the transponder antenna under the seats in the fuselage area and close off the hole in the back of the plane.
There are probably plenty of more suggestions on changes and/or additions.