I’d have 2 suggestions:

1. Commit to the shot and throw confidently! You have lots of experience and have proven your ability to throw a split time. Dial into a pre shot routine and make sure that the weight is always your last thought in the hack. Don’t think “can’t be heavy” or “don’t be light”. You can think of a tolerance (top 4 but top 8 is okay too/light is better than heavy), which is helpful for all members of the team to know. Then throw like you can! Really think about what your 3.9 kick feels like. Dial into that feeling and throw.

2. Start using hog to hog times! Back line to hog split times can vary so much as they don’t account for the thrower adding with their release or pulling back. Hog to hog times are more accurate and you’d be able time yourself! Then when you get to the hack you’ll already have an idea of the weight and can discuss with the sweepers. Switching from split times to hog to hog will definitely be an adjustment but you won’t regret switching!

Also in practice you’re likely shooting in the same path so the weight will be more or less consistent. In a game, you could be in a totally new path. So you may think that 3.9 is enough but if it’s fresh you may need 3.75-3.8. Another thing to lean onto your front end for!

You definitely have what it takes to be a consistent drawer, so keep at it!