Marshall the lane
Few years ago I shot one of the UKHFT rounds at Newbury. On the un supported kneeling lane there was a marshall stationed there for the whole duration of the competition to over see that the correct kneeling position was adhered too by all competitors. He knew the rules and wasnt affraid to pull people up for kneeling incorrectly. Thought this was a good idea and could easily be implemented into FT competitions.
As for slings I personally wouldn`t have a problem if a competitor wanted to use one. After all, if they give an advantage I could use one myself and so could everyone else if so desired. All just personal choice and whats in your head if you think it helps.