Thinking about the wing leading edge radiators, I did read on this forum that Hawker claimed zero drag on the Tempest I and maybe the Fury I. I, like the person who made the comment, find it a bit far fetched. If we look at those radiators compared to say the Mosquito or Hornet, as far as trying to get the drag limiting Meredith effect, the Tempest I/Fury I have small intakes, the radiators themselves seem to be aligned with the wing leading edges, and there doesn't seem to be much room for expansion of the air going into or coming out of the radiators, which is what's needed to get something out of the effect.
Also, the Mosquito and Hornet, being twin engined, ran larger radiators (one per engine), and the radiators and their intake/exhaust seem to stick out a lot further ahead of the front wing spar (where the assembly attaches). Of course, being twin engined and having thicker wings than most single seaters, the Mosquito and Hornet do benefit better than I think a single engine aircraft would. You still can get drag reduction though reduced frontal area, but I don't think that such an arrangement is great for trying to exploit the Meredith effect to try and reduce/offset aero drag.
Not to mention packaging. On a single engine fighter, the main landing gear is in the wings, and is also usually a popular place to put fuel tanks. To run leading edge radiators, you'd need to have the front spar close to the wing leading edge, and that usually means having the landing gear mounted behind it. Which means that the gear bay takes up space for a wing mounted fuel tank. One solution could be have the leading section of the gear bay (ahead of spar mounting) form a false spar.
Another thing that I consider maybe both a blessing and a curse for the leading edge radiators is that you'll end up with two of them. That could be a bit of a blessing as it could maybe give redundancy (like on the Me-109G's wing mounted radiators where if one was damaged, you could divert all coolant flow to the good radiator), but you also have twice the cooling matrix, twice the plumbing, and the other aforementioned packaging issues and potential limitations.
So I guess this is sort of maybe horses for courses. Maybe for a single engine fighter a ventral Meredith radiator is maybe the best all round packaging deal. While on a twin, Mosquito and Hornet type radiators probably work best.