I agree. After doing a fair bit of intense teams racing and match racing training (in dinghies), I recommend lots of starts and short(ish) courses, say 10 mins for two windward leeward laps (for cats), then do it all again.

Reasons for this is that it keeps all the boats close enough together to enable boat speed and boat handling comparisons to be made. If the courses are any longer, boats get too far apart to make valid judgements (problems with viewing distance and different winds).

Personally I would concentrate on boat handling (accelerating fast after manoeuvring/starts) more than boat speed as you can make 5-10m gains with good tacks, mark roundings, sets and drops. Do those 10-15 times a race and you can see that it adds up significantly.

I find that with boat handling practice comes a feel for your boat and with it will come good boat speed.

Please note that short course training is not meant to be comfortable, it will make you work hard and concentrate hard which will be good for your sailing. It will also force you to keep your eyes out of the boat, crew looking at wind and boats, skipper looking at wind and waves, which will again make you feel your boat rather than analyse it.