Re. Hydroplaning (Aquaplaning in the UK).
Main wheel tyre pressure, since these are the ones that are going to stop you.
Another important factor is the depth of tread on the tyres. I've seen a lot of tyres with less than 2mm of tread remaining in service. If the water has no where to go then there is more chance for aquaplaning to occur.
Hope this helps.
Glue ball. What a sensible A/C the 747 is from a line maintenance point of view. All 18 wheels the same and interchangable with the same tyre pressure, verses the DC10 with 2 different wheels and 3 different tyre pressures. ( early '80s when I worked on them).