I find it actually gives me a more stable kneeling position than using a bag, there's no question about whether my position is legal or not because basically it's not possible to get into an illegal position when using one.
and that for me is the problem, it will makes the disciple of kneeling less of a challenge to the point with anything, bag or roll to support my weight under my ankle I become as steady as sitting.
This will lead to scores getting yet further compressed.
Next, full size kneelers to 55 yards and hopefully, 25mm reduces out to 30 y kneeling
There was no problem with bag to keep the knee clean only, no extra faff to carry (not bothered about weight, its bulk) and my knee is protected in summer!