JumpingMan wrote:
Some friends of mine are obsessed with the idea of buying weather
balloons, filling them with helium, attaching them to a harness (with
probably about -3 to -5 lbs of net lift) and jumping up into the air.
If anyone has info on both the feasibility (with implicit danger) and
cost of such an excursion, you input would be most appreciated.

Several years ago I was into ballooning. One time we were approached
by two parachuters who wanted to jump from the balloon basket. One of
the group knew how to manage this and the two were able to jump from
about 5000 feet. It was necessary to establish about a 500 fpm descent
prior to each jump so that the weight change would be handled.