WARNING: I'm leaving this post up for now, but experience has shown this is actually a very bad idea. Although the hooked pads do improve adhesion on Hexon, they also exert a vice-like grip on felt roads and templates. Simply adding another paper label to the underside of the blocks provides quite enough friction to keep the them in place on 2-tile high Hexon slopes. 29 January 2016
I've used my ceramic blocks with flat Hexon tiles before, but not with Hexon hills. I was just setting up a game when I discovered that the blocks slide down Hexon slopes like an ice-cube on a hot tin roof.
I subsequently bought some self-adhesive hooked pads designed for gripping textile surfaces. Partly for reasons of economy and otherwise to minimise damage to the Hexon, I cut these into quarters and applied them to the backs of the blocks. A small amount is quite enough to get a grip on any Hexon incline.
My steel-based figures have more traction, but any future Hexon slope purchases will be of the 1-tile-high variety rather than 2-tile-high type in order to minimise the ski-slope effect.