As a fellow longboarder ... and on a smaller lake ...
Why do we use longboards ?
1) flotation in very light winds AND windshadows ie much more than 110 liters
2) able to head upwind and get back home with centerboard ie not a shortboard
3) able to go in light winds without schlogging about...
4) best suited for a smaller lake with lighter winds and windshadows
5) and thus the most fun on a lake
the issue these days is - what is a decent replacement
i have asked this question here already, butt in terms of a heavyweight
perhaps for a lighter person like yourself, you may have more SB options
Roger is the man and i hope he chimes in