I asked this question to the Helena FSDO about 10 years ago. Here is the part of the inspector's reply that answers my question:
"......there is nothing in Part 91 that prohibits you from securing snowshoes or any other cargo to the wing struts of your experimental, Part 43 does not apply to experimental aircraft, so if there is nothing in the aircraft's operating limitations prohibiting you from doing it, there is no reason why you can't. Although I am sure I don't need to tell you, but if I didn't I wouldn't be doing my job, if you decide to do this please follow:
1) stay within the weight and balance limitations of the aircraft
2) secure the cargo in such a manner that it will not come off in flight and if it should come off in flight that it will not hit and damage the aircraft when it does.
3) Keep in mind the aerodynamics of the aircraft and don't position the cargo so that it will disrupt airflow over the wings, tail feathers or flight controls.
4) If you install any permanent type of rack or tie downs, please make a log book entry to document the installation.