I put mine to the side because of your reasoning. Didnt want to put vertical in middle of frame as i didnt want to restrict air flow to front cylinder.

Mate there has been plenty placed on the bottom with no ill effects

if ya don't like the side mount then stick it down the bottom

Ive had a HD oil cooler on my 2014 Wide Glide since new. Its good. Its mounted down low below the regulator. It hasn't suffered any damage but I can say the middle few fins have lost the paint. Now I'm honest in saying I DONT ever ride on dirt roads but up here its impossible to dodge all the rain. So I can only say that must be the reason for the paint loss. Its like a vertical line of paint fade right in the middle. When I do more customising I reckon Ill move it repaint it and give it some braided oil lines. Its good where it is but I reckon it would be even better up higher. Fucking roads get blistering hot up here, so every bits gonna help in my view.
Stay safe you lot.