What to do with the “clear ahead boat “ that luffs his jib to slow the boat so as not to cross the line to early?
This can get complex....
If one boat is luffing close to the line that likely means they are early. As the goal is to get to the line 'on time and at full speed', it is unlikely if he is stopped just short of the line for any other reason. If you are timed well and he is on your line, you have a decision to make. You have to figure out how far down the line he will need to turn down to build up speed. If its a lot, go above him and take his place. A big gap will open below you where he was. If it looks like he will just 'trim and go', then go below him, and then use the gap below you as you gas pedal to foot for speed. Remember, you always want the bigger gap BELOW you.
A larger group of boats luffing near the line is a One Design tactic called a dial-up. These boat will sit next to each other in a line luffing just below the line, then trim in and go just before the start. This takes great skill. Fleets like Laser to J22s do this all the time. Obviously is it very hard or impossible to get into the middle of this line once it has formed. But you rarely see this in handicap racing; the different performance capabilities make it bad for the slower boats.
But in the right conditions you can mix it up.. We recently had a ratings banded race where we started with the faster more nimble J22 fleet, which contains two national champs. But the breeze was good for us so we stuck BlueJ right in there and dialed-up with them!