Each sun deck has a table and chairs - and a parasol to enable instant shade if required. They are those huge parasols which are fine on still days but in the slightest breeze they threaten to take off.
I think I have solved the problem by equipping each parasol with four guy ropes and tensioners which hold the whole parasol and table system solid as a rock:
We have very strong railings round the top of the former water tank onto which the distal ends are secured so the guy ropes are well above head height. You could not do this without four tall securing points near to the parasol - as with a walled patio maybe. The umbrella has to be raised underneath the guy ropes. The actual ropes are parachute cord - 4mm diameter, strong and with a slight 'give' to them. I got a 100m drum of it from a military surplus site on Ebay for about £8.
On the top of each parasol is a large plastic boss with a long bolt beneath it - ideal for fixing the guy ropes centrally and strong enough to take the strains. Today's parasols have easily replaceable covers in all diameters if the originals rot or fade.
I have abandoned those winders which are meant to raise the parasols. They never last. I did however retain the small pulley at the top of the mast for use with a bit of dangling para cord to assist with raising the canopy.
Obviously, out of season the parasols and ropes will be stored under cover.
This shows the system in action on a cloudy and slightly windy day. The guy ropes not only hold the central pole rigid. they act as steadies to the erected canopy: