Welcome to DRN, always nice to have another member interested in this part of the board as well as moto.
As far as the shots I think you did well to get what you did with the lens you were using. Having a variable aperture lens like the 55-200 that ranges from f4-5.6 through the zoom range makes shooting an AX darn near impossible unless you get real creative and shoot low shutter speed pans etc. That is one of the reasons you see the pro's with the big money constant f2.8 lenses. That 55-200 will work much better for you in good light outdoors this summer.
One other thing I always try to keep in mind when shooting sports was something I read on a photography forum when a new shooter asked a well know pro some tips. The advice was "shoot tight and crop tighter". Obviously this doesn't apply in all cases depending on the effect you were looking for in a shot but it's something that would help the shots you've posted in this thread.
I look forward to seeing more of your work as the season gets rolling :cool: