With the old Nacra 60 + W1000 modifications, we carried huge spinnakers that were difficult to handle. There were two approaches that were sometimes combined:
1. Smyth designed Harken Build "mickey mouse" ratchet blocks. It was an autoratchet block with two smaller blocks that made sure the line made contact with the ratchet for at least 60% of the ratchet block. Personally, I found them awkward in slow wind and ultimately took them off and stayed with a normal ratchet system (even the autoratchet system was not necessary since you usually know if ratchet makes sense before you start the race)
2. Changeable 2:1 or 1:1 system. Put a small line and two small blocks attached to the clew. Then put a cap cleat to the back beam of the boat (or nearby the spinnaker sheet block. You feed the sheet (from each side the same way) from the spinnaker rachet block to the small spinnaker clew block and then tie a figure-8 knot. If you take the knot and put it into the cam cleat, you have 2:1. If you release it from the cam cleat, it goes to the end of the spinnaker clew block and stop, thereby creating a conventional 1:1. Note, you can only do this on one side at a time unless you have huge amounts of line-- not advisable.