I do not understand the "width <= 80 cm rule" for your races.
Never heard of anything like that before.
Do they have "classes"?
With 50 sailors I would think so.
If you want to do well in these races, look around for an older Sonic W75.
That'a a board that truly rips. Won't plane as early as your F-Type, but it meets the
Beyond that, maybe something like a Rio M or Phantom would work in your situation.
Do they have a sail size rule also?
Maybe a larger rig would help get you going sooner.
Also, keep working on your pumping skills.
Sounds like you are still "following the fleet".
If there are smaller narrower short boards (without centerboards) doing well in your races (you seem to want to use your C-111 and that would not like your 9.8 very well,
and it reqiures alot more wind to get planing) then take a look at what the others are sailing and maybe we can suggest a Starboard that would do better for you.
Are you saying that the sailors at the front of the fleet are on 80 cm wide shortboards, but are not planing at all, but beating you on your F-Type?
This is very puzzling to me?
Also, it sounds like your "slogging" skills could use some work as well.
You should be able to stand off center on the F-Type and "bank" or rail your board and
stay with other shortboards pretty easily. You won't be able to stay with longboards (with centerboards) short taking upwind, and not on a beam reach in less than planing conditions, but I think you would be able to stay with short boards on a figure 8 course.
Is this course laid out truly across the wind with the pins (buoys) parallel with the starting line so you sail across the line and then up to one or the other of the buoys, then figure 8 around the buoys, then head back down to the start finish line, or some other setup?
If the bouys are truly "across the wind" and you are on a beam reach (about the same as most "back and forth" windsurfing) I would think you would be doing quite a bit better on the F-Type and perhaps this is why they don't allow wider or formula type boards.
Hope this helps,