In reply to wbo2:
I think my 'natural' running 'style' is landing flat on my feet
About 4 years ago I got some cheap (Karrimor) running shoes to try to get fit in the winter, ran only on tarmac paths (dark & damp), tried to stride out a bit more in the hope of rolling my foot from heelstrike over to forefoot. Although the shoes seemed to have good cushioning at the heel, after a few sessions my ankles ached badly.
My locally available off-road circuit is 2k of old railway track & farm track so it's firm but uneven & varies from light mud to packed earth and stones. This is followed by 1k up & downhill on softer track/farmland/grass then about 1k on tarmac back home. I can drive a mile or two to two local parks, mainly grass with some gradients, one with some steps & earth tracks. I use La Sportive Ultra Raptors at these venues as they fit me well.
I've tried to improve dorsiflexion with stretching, with no noticeable change in forward flex, but given up due to ankles aching again.