The drillings (3 holes right) are for the optional side fins.
This board was designed to get kids sailing on one board right from
the start.....so, the side fins were for the early stages of slogging along.
As soon as the sailor progressed to planing the side fins were to be removed.
Here's a link to the 2003 website that explains all about the Junior Formula
It's ASA skin makes it a bit heavy (11.63 Kg.)
By todays standards, it's small, and heavy, but I had one and it was pretty fun.
Not sure how it's going to work for a fellow your size, but if you have more than
12 knots you should be fine.
It's actually a few more liters than 136.
Hope this helps,