Helmet tips...
So....my noggin is the shape of a watermelon and consequently my 'new' Davida helmet has a few pressure points that I want to soften. The inside core is just styrofoam, albiet quite compressed. I am thinking, llike a surfboard, I can shape the foam core a bit with just some sandpaper. Anyone out there try this out yet, or am I delusional and about to destroy an expensive helmet?
There hasn't been a helmet I haven't reshaped fractionally. The key is to find one close to the shape of your head. In the world of sport bikes, there are different head shapes and therefore different allegiances to different brands of helmets...Arai head versus Shoei head yada. I have a long oval shaped head for example...narrow but long front to back and Arai makes a helmet that fits this.
There are many schools in reshaping the styrofoam and Ryan mentioned one of them. I don't come down quite this strongly as a...motorcycling is no fun if your helmet doesn't fit very snug wlth inner shape matching your head and b...if you don't take off much material, then there will be little influence on protection which all depends on the hit anyway. A little tweak can make a big difference in comfort. I only ride full face helmets to maximize my odds in a crash but that is a different discussion.
Your two options are:
1. locally sand the foam for the hot spots
or
2. Compress the foam for hot spots.
I am of the school that compressing is better than sanding because volume of foam is conserved but either will fractionally reduce impact protection.
A good starting point is identify your hot spots and either use a spoon for localized pressure or your thumb to locally indent the foam.
The best tip I can provide is don't be overly zealous in getting the fit perfect with compressing or sanding. The reason is the foam will assimilate to your head shape over time. You may curse the helmet initally and then after riding for a couple of months forget that you even have it on. As a result many buy a helmet too big by trying it on in the store and it feels more comfortable than the next size down. Big mistake...literally. Helmets loosen over time and best to buy one a bit snug as it will agree more to your head shape the more you wear it.
Hope that helps.