On Sunday, September 17, 2017 at 5:32:43 PM UTC-7, wrote:
Has anyone done a 337 to modify a Std Libelle with the Tost 4" wheel? Looking tech data for a 337 or a precedent of someone that has already done this. I know the Tost Wheel Selection Chart shows compatibility and Streifeneder is ok with the substitution but that's probably enough to satisfy the FAA.

Uh this has accommodation for a 4" wheel already right? You are talking off one tailwheel and replacing it with another, maybe with washers or axle spacers? Right?

What major modification is being made here and who is telling you a 337 is required?