Conditions have a lot to do with the relative advantage. When the conditions are fairly benign the advantage to Open is less, but when it gets lumpy the Open needs about 1/3 to 1/2 less windage of the TR.
I shot a 2 day mid range match recently in TR where the conditions were not particularly challenging. I tied the #2 finishing F-Open shooter on score and was one point behind the winner, but I only had about 2/3 the X count of either. Had the winds been higher those dropped Xs would have become dropped points.
Exactly so. When looking at GB F-Class League results posted online at the end of a day's competitions for rounds that I've not attended, I can tell how hard the conditions are simply by comparing the winners' aggregate scores for the two classes. If benign, they are fairly close; if hard the gap jumps two or threefold.
That is for aggregates with individual stages shot at a minimum of 800, maximum of 1,000 and the longer distance offering more points through 20-round courses of fire against 15 for 800/900 yards.
Last year's individual match aggregates for the F-Class European Championships meeting at Bisley were:
FTR ........ 464.30v to 467.31v for the top 5 competitors. (Our 'Bull' scores 5, so HPS for the 100 round agg was 500.100v, the 800/900 yard matches being 2+15s, the 1,000s 2+20, two shot at each distance over two days.)
F-Open ... 476.39V to 480.44v for the top 5.
Just looking at those scores told me that conditions were (relatively) 'easy' long before the write-up appeared given the 'mere' 13 points between the class winners. In 'hard' conditions, that would have been 30-45 points on the aggs. Sure enough, when the write-up came, Des Parr described the conditions as abnormally steady with relatively light winds for Bisley in September. On day 2 not only did several FTR shooters 'clean' the 800 yard stage (not unusual especially if FTR is assigned the first relay of the day before the winds get up), but two FTR competitors 'cleaned' Stage 5 at 900 which was unprecedented.
Our annual 'short-range' league round (4 matches at 600 yards at the very tricky Diggle Ranges) early in the season and usually subject to dire upland weather conditions still sees F/O hammer FTR every year.
On only one occasion ever, do I remember the FTR winner beating F/O in one of our national league rounds on aggregate. That too was at Diggle in unusually good summer weather conditions. The reasons for this turnaround were that Russell Simmonds World FTR Champion at the time and in really sparkling form that weekend had the added bonus of a freak calm in one of the two 2+20 1,000 yard stages and either cleaned it or only dropped a point. When it was F/O's turn, the conditions had changed enough to see the class winner drop several points.