You won't have biconicals from Portland.
They were never needed.
Portland has chesil beach, about 5 miles of the best slingstone beach i've ever seen.
There are pictures on the forum, don't think I've got them on this phone.
But yeah that's why it was called slingers isle, because of the pebble beach.
With an unlimited supply of perfect ammo, it would have made sense for slings to predominate.
It was one of the places we went to on the slingers road trip

The isle of Portland is more famous for Portland stone. Which has been quarried there since roman times, I believe.