I didn't have the seal and the bonnet was set slightly high to permit heat to escape all round....
All can add to the cooling effect.
I found when driving normally I had no issues. When crawling on lanes etc. no issues. Stationary no issues....
I put the holes and extra cooling in just in case I was sitting in mud etc. and there was no air flow under the vehicle at all...
When it came to a 2nd gear low crawl up 7,000 feet of mountain tracks I had to stop several times to cool the engine. On reflection I think I may have gone too oversized on the radiator and too large a reservoir of water. Basically I had water storing heat (Energy) and the engine always making more but my capacity to dispel that energy was too low.... With a smaller capacity radiator, I would have been storing less hot water, less energy, and would have probably been able to maintain a bit more of a balance overall.....
It was a moderately tuned 4.6..
Apart from that, every little helps to get hot air out of the engine bay....