Reaching trim

If you pull it in further, you simply create more heeling moment, so it may well feel faster, but I doubt it will be. What may well be faster is luffing in the lulls to keep the power on, then bearing off in the gusts to keep the boat flat without having to spill wind, rather than going in a straight line.

Another way to do it is to use leach telltales. The sail should be sheeted until they are at the point of stall (just getting agitated). This in my experience works well and generally gives a more sheeted in sail than from working on the luff lifting. It also helps to set the vang as they should all break at the same time if the vang is correct.

On a beam or broad reach where you are looking to generate maximum power from the rig you want good airflow over the sail which is just starting to stall as it comes off the leach.  This is not easy to achieve and involves sail shape as well as sheeting angles! Like oatsandbeans says leech streamers are usually how I try to achieve this.

I honestly don't get all this, watch the tel tales, I think they are a total distraction. In my very early days windsurfing back in the late seventies, when any dinghy waller who was worth his salt was coming over to give it a go, they all came with their rigs with tel tales all over the place, so I fitted them on mine. This was in the early days of what became Division 2, so there were CYT sails, needlespar masts, experiments with boom vangs (to emulate the kicker) and topping lifts (something I tried to overcome the stupidly stiff rigs they came with so the top of the sail would twist off).
But the thing that came out of it and this was before we were pumping a lot, was whatever the tel tales told you was the optimum position according to popular consensus, was rubbish to produce board speed and the only really reliable means of telling was feel, and that was out of the harness feel, and so it was us guys that had sailed windsurfer class OD where harnesses were banned anyway, came to dominate in those early days. So the crux of the matter, feel does it every time and that has been the most difficult thing to achieve in the ten years or so Ive been blundering at this lark.

Without that essential connection direct to the rig you are so lost, I'm beginning to get a bit of feedback through the bum and I use all those other pointers, stern noise, feel through the rope (never cleat it off ever), even the sag in the lee shroud, plus the wind in your ears and knowing wether the puff is a lift or a header and making sure you act accordingly especially offwin where it's more difficult to tell, but it is so so much more difficult to pick up, especially if like me you don't practise other than to go out racing, I guess if you spent a bit more time in the boat it would come quicker..

iGRF is actually right on this (never thought I'd say that). With a board you have the great advantage that when sheeting in the sail with your back hand you have an immediate feedback of how much aerodynamic force is being generated. So as you sheet on you can feel when the sail stalls as then the load drops dramatically,then you sheet out until the load comes back on as the flow reattaches. The old Div2 rigs with long booms were perfect for this as there was so much feel from the back hand, no need for tell tales at all.