I used SimpleAI to put some more traffic (Lancair Legacies) into the air. This worked fine......but I always here on the ATC "Expiremental on final" and then when they're about to land "Expiremental is going missed". It doesn't do this with the default AI. Any suggestions???

No I don't think this is the reason. If there are insufficient parking spaces the plane just lands and disappears.

The most common reason for this is that the FDE of the aircraft is unsuitable as it stands for AI. Usually it's because there is too much lift in the model and it can't get low enough on approach to 'capture' the runway. Remember, AI work to totally different rules to flyable aircraft!

If you don't feel confident enough to start editing air and/or cfg files the easiest thing to do for starters is to swap the FDE of the addon aircraft for files from a default - Legacy will probably be compatible with a PA28 or 172 (is it retractable - I dunno - if it is use the files from the 182RG)

Just try copying the [sim.0], contact points and lights sections from the original cfg file into the cfg file from say the PA28 and see what happens.

post the flight plan line for that flight.

It seems that most military planes to actually do a Touch and Go need to be an VFR flight plan. If they are IFR they do missed approaches.

Experimental has been answered above