I know stiff decks are more popular here, but does anyone have a recommendation for a roughly 34" deck, with a good amount of concave, and similar amount of flex as a Boosted/Vanguard Flex 3?
That seems short for A flexible deck.
Like @Skunk said the loaded board is flexible because of the size and the material used. The deck is 38 inches with a wheel base of 31. With a 34 inch deck you are looking around a 28 inch wheelbase. This would probably be your best bet https://www.muirskate.com/longboard/decks/32671/loaded-poke-longboard-skateboard-deck-w-grip
this deck has close to no flex for me ><. I’m only 160lbs though.