Yep, your spot on, it's still worth the effort to change. a simple 1/4" plate drilled for the 1 1/4" cassitte could be welded to your 3 hole and easy to touch up. One trick I use is 4 bathroom scales, 2 under the front spindles after you have set then both the same height, then tack the rear axle in, place it over the 2nd set of scales and adjust them up or down from neatural until you get what you want, I personally make sure I can get more left side weight than right. Even if you think the frame is straight and equal, most times it is not.