***Which begs the question. How well balanced are the F/A ratios (assuming good ignition, no induction leaks) in the average Lycoming O320 O360 IO360?
What I'm interested in is how practical is LOP for the average pilot flying a C172 or PA28 or anyone flying a four cylinder Lycoming.***
For a growing number of carby pilots in the US this is becoming standard operating procedure. Each carbed engine has an optimal carb temp that results in the optimal F:A mixture being delivers equally to all cylinders. This temp is actually given in many POHs (often in the fine print!) Once this temperature is identified, it becomes very easy to set the carb temp to that value and have very good fuel vaporization which results in even F:A ratios and the ability to run the engine much smoother across the entire mixture spectrum. For example, in most 182s, the optimum carb temp is 10dC. Each aircraft type tends to have it's own optimum value. This was once considered standard operating procedure on carbureted engines but the technique was lost. It is very difficult to find this optimal carb temp without and EMS, but with one it is very easy.
In the IO engines, the F:A ratios are balanced by tuning the injectors (GAMIjectors).
As for "legality", there is nothing I can imagine that would be a problem since the entire mixture curve graph is published in the POHs. If the POH recommends 50dF ROP and you run it 100dF ROP, is that a violation?