Shrouds and mast rake...

The position of the shroud in the side chain plate is dependant on the shroud length, main block system and the amount of mast rake you want. Typically more rake the better on a 16.

This will be trial and error on any boat as the size / height of the blocks vary, wires vary and frames vary (such as forward crossbar bend, striker tension). Adjust till the mainsheet blocks nearly touch when fully sheeted when sailing.

Adjust the shrouds. Tension the jib halyard to pull the rig forward and tight. Sheet the main, tight as you would for the days sailing. Look at the main blocks, the distance between the boom blocks and main ratchet set. Too much space? loosen the jib halyard... Move the shrouds down a notch or what ever... Tension the jib halyard again... Check the mainsheet tension and gap. Repeat if necessary.

If the main blocks touch, you will not be able to sheet correctly when sailing. Reverse the process and move the shrouds up a notch.

P.S. the forestay wire is only for rigging. It goes slack when the jib is tensioned. The forestay should not take ANY load while sailing. The jib luff wire should take the entire load. Otherwise the jib will bow off to leeward and upwind sailing will be more difficult. You can hold the wire with a small bungee so it doesn't slap the jib while sailing.