Anyone who says lasers are the most fun you can have on the water are deluded! Its a bit like saying Carrera are the best bikes as there are loads of them.
RS300 is a great little boat, but at 10 stone you’d probably need the little sail.
The RS100 is still quite new and you’d pick up one now for around £4k, but I suspect to get the most out of it at that weight you’d need the smallest 7.4m sq rig and they are still quite rare.
What about a Solo, perhaps not quite as fast as a laser, but more a boat than and ironing board. I’d dare say possible an even stronger class for anyone over 25yrs of age.
Personally i’ll be sticking with my Musto Skiff for a little longer yet ;-)