Yep them AA5's like to float if you don't get your speed right.
As for the shimmying it i usualy down to 3 things.
1) Taxying to fast
2) Shot nose wheel bearing
3) Bearing on the caster (if thats what it is called)
The bearings being shot are quiet common on the AA5's.
Other than that great aeroplane. Unfortunatley the mong that fly's mine now and again took the prop and engine out by duffing up a cross wind landing and failing to go around!