I have a masthead rig which originally had a wire backstay with no means of adjustment. Where this was split to the two anchorage points on the transom, I have replaced it with an adjustable rope and pulley system.

At the split, I have a single pully block, with the rope being anchored at the transom and the other side of the block leading to the adjustable pulley system. This has a double block at top and fiddle block at the bottom, the latter having a cam cleat for locking off.

This system will allow tensioning of the backstay and forestay to tighten the luff of the sail when beating. It can then be released for downwind sailing. It will certainly give better adjustability and improved sailing qualities.

I am sure that my system is unlikely to suffer any failure, but to be 100% sure I have left one side of the lower backstay connected with a wire backup.

Hopefully the pictures will help to illustrate my explanation.