It's simply physics. The boat was designed for a slightly larger person. Don't get me wrong, there are some smaller guys that can really work the boat and do well. However that takes years of experience.
When heeled, your really slide down a lot to windward. One thing to try is maybe not two-block the mainsheet and point off a bit. You can keep the boat flatter, and won't slide to windward as much.
Slide to windward???
That's a mistake, obviously.
I have similar problems with the full rig at 150 lbs. The 30 lbs does make a difference going upwind, but it may give you an advantage on the reaches and runs.
The guys who really know Lasers tell me that sheeting out and keeping the boat flat is faster than sailing fully sheeted in and closer to the wind, but heeled.
Making that work is something I still have to learn. But as they say, time in the boat is all that matters...
Just my two cents!
As has already been mentioned you are a little on the light side for the standard rig although I am surprised that you are finding yourself that badly overpowered in 10-12 knots so I would suspect it is more a case of technique and sail set.
How much Outhaul do you have on, as a general rule of thumb the advice I have been given and always used is to have a stratch hand span (tip of thumb to tip of little finger) as the maximum sail depth in conditions where you are looking for power and the width of a clenched fist when it is light and when you are overpowered.
Too much outhaul can lead to excessive healing just as easily as too little.
If the cunningham cringle comes down to the boom with relative ease it is also indicative of a stretched sail and you may need to pull is on more. On a particularly blow out sail i used a few years back I could get the cringle down almost below the gooseneck.
Once you have sorted your outhaul then it is kicker and cunningham all the way. Using more of each until you are overpowered and then ease the kicker but never any less that 'block to block' when going upwind.
I am guessing that off wind you have no issues?
The other thing you might want to try is to swap boats with someone else in your fleet for 1 day or for 1 race just to see if theirs is different and see what they think of yours. It is surprising how different boats can feel and how a different sail feels (this would give you a good indication on if your sail is blown out or if you are just too light).
Above all practice, especially with the technqiue. You can either foot off in the gusts or feather the boat up. It generally comes down to what the waves are like. On flat water feathering the boat into the gusts can owkr well, in waves you need more power so footing off it better.
At my local club (which is flat water) there is a guy who is about your weight who is fast in all conditions, he does have to work the boat hard though when it gets windy.
Slide to windward???
Excuse me. Slide to leeward.
I agree the problem is probably more with your technique, I'm around the same size/weight, my vang is setup for the max to be more than block to block and the cunningham to the starboard side so max on is down to the goosneck. If your hiking strap is too tight you won't be getting the most from your hiking. Hiking pants essential. Keep your outhaul set so that the sail is at least 2 inches deep at the boom cleat.
Behing on the lighter side I've found using a combination of easing the main (up to 3ft max ease) with cranked vang and cunningham while hiking hard to keep the boat flat is fastest in higher winds (usually around 15+kts).