Shannon,
I should add that Dale Kramer really hated customer modifications to his design, like most airplane designers. Considering that I was one of the worst offenders back during his first couple years in business, I was always kind of surprised he asked me to come work for him. Over the years, with people making all kinds of changes and additions to their planes that affected them structurally or aerodynamically, some got hurt. The lawyer's bills started to pile up, and he came to dread hearing about modifications people would come up with.
Some that I remember: clipped wings for higher speeds and aerobatics(caused wing and lift strut failures and deaths), inverted wingtips (for more low speed lift, but reduced stability in turns), enlarged ailerons or full span ailerons (exaggerated adverse yaw making control difficult in marginal conditions), spoilers positioned indiscriminately on the wing, flaps (Dale got in BIG TROUBLE when a flap on a factory prototype experienced such sever flutter he was afraid he would have a wing failure!), extra tail surfaces, an extra engine mounted between the tail surfaces (gross CG problems, extreme changes in pitch control authority with large power changes, potential damage to the ruddervator's structure and hinges), multiple additional engines mounted rather far out on the wings (pilot workload, extreme yawing with an engine out), poorly designed pods and windscreens (that caused such downforce that at speeds below VNE the plane did not have enough elevator authority to pull out of a high speed dive). I'm sure I could come up with others. It's not that all modifications are bad or dangerous. It's just that they have the real potential to be IF they are not well thought out as to the effects on structure and aerodynamics. The implementation of modifications, as to how well they are actually done, is also very important and can make all the difference as to whether they are safe or not.
Ultralights in the USA are not certified airplanes, or even Experimental class, and as such we have an incredible freedom to work on and mess with them that no other class of airplane enjoys. As such, we have the responsibility to not abuse that freedom by doing too many dumb things.
Anyway, that's just my humble opinion... now that I'm much older and a little bit wiser.
Chappy