Tandem Island dual sheet line controls question

Well, OK I guess I have another dumb question

Excluding the furler line block; there are 2 Harkin blocks one for the front occupant and one for the rear that each has a sheet control line.

If the front passenger has the sail pulled tight (sailing upwind) and locked in the block how would the rear passenger ever make the sail looser? I guess the reverse would be a problem. It would seem like the ropes would fight each other. I'm imagining 2 single lines back to the pulley and clew.

I tried studying the newest pics from the boat show and got a headache trying to follow all the lines. Is there some clever doubling up of the line happening here that truly allows independent sheet adjustment from either position?

Dual tiller steering is easy to imagine steering lines in parallel, the sheet lines had me boggled.

Thanks

Yak, looking at YackMan's pictures, you'll see the mainsheet is a continuous line, with one bitter end in the front cockpit and the other in the rear cockpit. In the pics, the aftsheet is released (terminated at the cam cleat) and the foresheet is the operator (note surplus line sitting on the cockpit deck). For the aftsheet to be the operator, the foresheet releases, terminating against its cam cleat so there is ample sheet for the other end to take over. Under this arrangement the main would be operated by either cockpit, but not both simultaneously.

Structurally, you can follow the aftsheet running through its cam cleat forward to a block on the starboard side, then aft to another block, then up to the double block, then to the sail block, then back to the double clock, over to a second block on the starboard side, then forward to another starboard side block then back through the front cockpit cam cleat. Knots at each end prevent the sheet from slipping through the cam cleat fairleads.

Simplicity itself.....Ingenious rigging!