Hi S, I'm sure all suggestion will improve your situation, you want to know which is the most effective.
Without seeing these shoes I can't comment. We generally have foot bigger than the other. I suspect if one shoe has less room, then circulation will be slightly worse, so the larger foot becomes colder.
The reviews of these shoes are not entirely complimentary on the ability to dry out quickly.(bikeradar.com & off. road.cc)
I assume your are using full size guards & mudflaps, any wetting, (ingress or saturating the outer) , will rapidly increase the cooling rate of your feet. That from any surface area, upper or sole.
So one of my suggestions
Add a mud flap at the bottom of your front guard
(
But you've already done this right?.)
It really makes a difference & simplifies. cleaning...
A damp boot will be a better 'heat sink', thus cooling your foot more, So don't entirely dismiss overshoes. Your shoes will also dry faster. A bit of a faff, but definitely worth it.
Dry shoes = warmer feet.
Also to state the obvious, -
Don't fasten them too them tightly, it will Impair good circulation. Unlike walking, the whole foot doesn't flex so the foot has poor circulation. Make sure you have room to Wiggle your toes.
I know your annoyed and frustrated
with Mr Shitmano, but don't be 'short' or rude in your replies. These guys are only tryng to help.
Good luck D
PS
Failing that, Simon Mountain-feet, Marsden is, an expert at fitting/adapting mountaineering boot, he might have some high spec thermal innersoles. He fits guys (&gals) for Mont Blanc, the Eiger, Nepal etc. No breaking in £500+ a pair., never take off whilst on mountain etc. Just Gotta be right..
I hope you think you know, what I might of exactly meant.
Warning - may contain value odded typos & ither mythspellings..