Yep, when you're grovelling, you can't rake the rig back as far, because it's more vertical, there's a greater distance between harness and boom, you should be able to drop the boom to shoulder height, (or a tad lower), without a problem.

Quality adjustable harness lines are your friend... you will never look back

Might try some adjustable lines & keep the boom height as the conditions im talking about blow 5kts one minute & 20 the next..

I have adjustable lines. I used to adjust them regularly. Now I keep them fixed at the length I like and adjust the boom height if necessary. It only takes a couple of centimetres up or down to get it right.

Another suggestion is eat some weetbix!!

Get rid of your harness for a couple of sessions.. It will hurt like hell but you will be strong in no time.

I also do chin ups and push ups when your off the water. Keeps you strong for your next sail.

don't drop your boom. It won't make anything better and it'll take you longer to get planing - so more arm pain

Get a waist harness and when you feel the wind is falling away, tip the rig back gently and sheet out - harness should unhook and then you'll be fine

I haven't read all the other responses but I presume everyone has already suggested HTFU

i'm onboard with ginger pom.... hehe again.

definately don't drop your boom, should be shoulder to chin height. on big kit nose height.

a higher boom is a must in light winds. the difference to your early planing is massive.

what i do is jump to unhook as i'm to lazy to extend me adjustable lines.

also longer lines are needed in light winds. i run 28in on my bigger gear and 24in on my smaller gear. with seat harness....

having longer lines in light winds allows you to keep your rig upright and swing out taking your weight off the board.