We've stepped 420 masts with 15-16 singlehanded but were also quite fit race sailors. The recent kids coming from Opti certainly could not reliably manage. So I reckon not a lot of weight at all.Consider if I were a typical 14-year-old; that would be the safe limit if I were to follow orders in this scenario.
Agree with the Bravo being easy to rig. I know about one in Southern New Jersey that will be for sale fairly soon.The easiest boat I have ever rigged is a Hobie Bravo- 12 feet. No stays, the boat has a permanent A Frame for stepping the mast. The mast, masthead float and sail together weigh 28 pounds. But you aren't lifting 28 pounds, maybe half that. Roller reefing boomless main. It's a ridiculously easy boat to sail and rig. Its slow compared to other beach cats, but I have had mine into the 10 knot range, so not a total slug.