I am not sure if I agree that Lycoming themselves are the best source of information. Over the years I have dealt with many such problems, particularly with Para, Glider Tug, Crop dusting and aerobatic aircraft. The engine manufacturer lays down the limits, it is then up to the aircraft manufacturer to see that those limits are met. The aircraft manufacturer makes the cowlings, sites the oil coolers and the cooling baffles. So the aircraft manufaturer are more probably the people you should talk to. Having said that I have often found that the aircraft manufacturers are sometime surprised at what thier aircraft are being used for and in many cases not what they were initially designed for. I have worked on many different types used for glider towing that were clearly not meant for the purpose.
Siting of the oil cooler is particularly important. A typical fit might be inside the cowling fed by engine cooling air before it is exhausted through the cowl flaps or whatever. Engine cooling air by this time is already hot from cooling the engine, and thus doesn't cool the oil too well. On many occations I have modified Lycoming powered aircraft with a second oil cooler placed in the forward intake baffle in front of the rearmost of the two front cylinders. This modification was also carried out on numerous Pitts aircraft fited with both the IO-360 and IO-540. If this is already the position of your oil cooler then consider siting another in the way mentioned above, inside the cowling. There is sometimes more room inside the cowling that you can fit an oil cooler of almost double the size of the one at the front.
With glider towing and Para aircraft the real danger is in the sudden cooling of the cylinders in an idle power decent. The cylinders will crack. I have known the whole head to come off from the barrel, in fact the CAA still use it as an exibit! Aslo new engines or engines with overhauled reciprocating gear will run significantly hotter untill they are well run in, thus giving you the hot spots you describe. A further note is to consider ambient air temperature. Check your temperatures on the hottist of days and not when it's cold and raining!
Hope that this has been helpful.