I have always put toe-in into the mains of my taildraggers and trikes. I noted that the wire main gear tended to "wear" to give toe-out, so I would keep bending things to toe-in after many landings. My aluminum gear would likewise go to toe-out with usage. About 3 years ago I built a SPAD 72" WS J3-Cub with an OS46FX engine and 12X4 APC prop. It uses a carbon reinforced fiberglass gear that keeps the wheels neutral, ALWAYS. The angles do not change with usage. I have stopped worrying about the toe-in/toe-out problem. Maybe it is because it is NOT adjustable by bending the gear. I see nothing in the performance to indicate to me that toe-in/toe-out is needed. I am always amazed at how difficult the J3-Cub is to take off and land. That is probably why I like it so much. Do it perfect or it will let you know. I loved that carbon reinforced fiberglass gear so much that I used it to replace the 3/16 diameter wire gear I was using on my SPAD OS46FX size Pusher Canard. That plane lands hot on the mains and the new gear works perfect. So, neutral, if it stays neutral under load and usage, seems to work great for me. In my opinion, if toe-in or neutral goes to toe-out under load/usage, then there can be difficulties.