Where did you buy your halyard?
If like me you have bought rope cheap at boat-jumbles, you will know that you get what you pay for. I bought a lovely piece of 5mm rope that I thought was a Dyneema or Excell look-alike, only to find it had a fair degree of stretch and my bar-taut main halyard at the beginning of the sail was a floppy washing line after a couple of tacks. Excell and Dyneema are expensive for a reason, they do not stretch. Having bitten the bullet and bought the proper stuff, stretch is no longer a problem.
Taking a leaf out of the Hartley book (seen at a show) I pop-rivetted a lacing eye with a small block onto the mast about 600mm above the sheave in the mast heel and self-tappered an open clamcleat about 150mm below that with the teeth arranged to resist a pull down. The main halyard exits the mast and, passing over the clamcleat rises over the block and then down to a horn cleat screwed to the tabernacle. For speed the main is pulled up with the halyard outside the clamcleat, then once it is getting tight I put the halyard under the hook of the cleat so that as I am pulling the sail up the cleat takes the load. I OXO it off on the horn cleat as an insurance just in case the teeth of the clam-cleat get blunt one day and slip.
The genoa luff is tensioned using an 8:1 Excell cascade alongside the centreboard from a large deck loop screwed to the top of the centreboard casing. The front of the cascade has a steel hook that engages the loop on the end of the wire genoa halyard. The tail of the cascade passes under the thwart and is cleated to a cam cleat just behind the centre main block. Beads threaded onto the cascade save the centreboard and top of the casing from being scratched by the cascade blocks.
I have experimented with triple blocks (like an un-cased muscle-box) instead of the the cascade but find that the resistance through the individual sheaves mean the blocks tend to twist out of line, is hard to de-tension and anyway, two triples are much more expensive than the three singles of my cascade.