... as above finally found my grail piece but i can't believe how quickly they fog up !.. Am i wrong to think the Hydrophobic Lens Treatment is what i need ? I used to rub a slight amount of washing up liquid on the inside of my motorbike visor and that worked a treat but somehow that feels wrong to do with O's... :)

For the most part - you don't.

One thing to try is add some thicker foam on the inside of the frame where it hits your forhead above your eyes to keep them off your eyes a bit more to allow better circulation.

Nik's suggestion is really the #1 best bet in my book. My 2 OTT are slightly different - 1 has the frame cutout with the foam insert and the other has no frame cutout, so the foam insert pushes the frame a bit off the forehead and ends up fitting so much better with less fogging.

The hockey anti-fog solution might be another option?

Otherwise, you'll also find just some slight alterations to how high or low you wear it will affect how easily it fogs.

thanks guys for the suggestions !,i will look into that mod asap !!