I use the standard 4 supports, and since most of the weight is on the keel, this hasn't appeared to put any undue stress on the hull. The boat has been on the trailer for all of its 20+ years and has no indents at the pads.

However, when I bought the boat there was significant blistering under the 4 pads. Beware using house carpet as it traps too much water underneath the pads during the long winter months and can lead to water intrusion.

Other folks have suggested various better materials, from astro-turf to ribbed rubber to help prevent trapping water against the hull. Just something to be aware of...

--brendan