Don't know how long you have had your SC but here's a shot that should help you:
http://i96.photobucket.com/albums/l172/ ... arview.jpg
http://i96.photobucket.com/albums/l172/ ... rtDown.jpg
Now here's the long and short of it. We boat on the Potomac river, and the 2100SC has really been great. The problem always was that late in the afternoon when returning from a distant location when the winds would pick up the boat would pound across the chop and I would have to constantly twiddle the outdrive trying to find the best angle to chop through without loosing my fillings. I went round and round on the decision to tab or not to tab and when I finally broke down it was such an easy install that I couldn't believe I hesitated. Now the ride report. The Lenco's you see installed were the 12x9 edge mounts with the NON indicator switches.(extra 200 bucks really not necessary your gonna place them where the ride is best not the light). I want to emphasis that I mis mounted mine thinking I needed more down where as you really need very little deflection below (in the down direction) to make a difference. What you are gonna need is plenty of up to get out of the way.
The tabs will make the boat behave like it is a 23 foot boat not a 21 foot. On the straight they will help keep it carving through chop. Even up they will INCREASE your top end (albeit very slightly) Here's the bad news, especially for me, they will reduce your turning radius. I can't get mine up out of the way enough....
The wandering you describe is normal, and putting the tabs down does slow it a little, but for the most part it is just what you are going to get with a prop that is turning and wants to walk the tail to one side.
For more information on 2100SC mods see: http://sempreveloce.tripod.com/