I have a 2002 H410 and spoke to Selden...
because the rubber collar at the top had spread around the top fitting and was wedged in such that it pulled out of the main vang tube. He said that the vang was incorrectly attached to the boom to do this as it was never meant to support the boom (unless you have the gas cartridge added). They were very helpful, sent me the replacement collar for free on the condition that I would change the boom connection position from what the dealer had installed. What I was told to do was, in slack wind, to release the vang, remove the screws holding it in the boom track so it would slide freely, pull the main all the way out, and then tighten the mainsheet fully taught. He also said to tighten the topping lift to this same setting. This puts the boom at a maximum low point. Note that the screws only hold the slider from sliding and do not need to be tapped, only drilled enough for the bolt to pass through. The next step was to mark the place on the boom where the vang fitting would still leave the vang about an inch above the collar. Then redrill so the bolts will hold the vang slider at this point. No problems since doing that. If you do not have a Selden vang you might want to call the company for your vang to verify proper installation position.