Took out the Cabrinha 183 with 16M crossbow yesterday in 12 kts.

I'm a former windsurfer so i get the whole driving on the fins thing and by the end of the day I could go upwind and downwind by riding the fins instead of edging, but i was completely overpowered...in 12 kts. Full depower strap, didn't take the kite below 45 deg.

You have to remove everything you think you know about kiteboarding. There is absolutely no way to mannage power using the board. You can't turn down fast enough to blow power that way and if you turn up the power increases.

Any tips?

What do i do with the footstraps? - I tried using them windsurfing style where just the front of your foot fits, and my upwind was insane but I had very little control. As I opened the back strap up and the back foot moved in I feel like I gained control but lost upwind ability. For going downwind I found riding in the opposite(leeward) strap was easier.

I guess practice practice practice is the plan...

Isn't the purpose of a race board sort of balls to the wall speed?

Yes, and I got that, it's just I had no control whatsoever...
Extremely unforgiving.

It felt like stepping up from a smart car to a F1 Car. I was happy just to get it around the track...

I can understand that completely. The other day I was riding an Airush Sector 60 V2 and a SS turbine in around 12 knots, totally juiced. Around my location, light wind is never light! It makes it very challenging to get the right kite size. Using that board I tend to rig for the gusts not the lulls.

There are some videos of that combo.

This one is a bit hairier

Take a look at the Race forum section for more info on your Race board. I am just starting to understand mine too, not easy at first but should be fun once we manage to dial it correctly

can't you take a foot out of the straps and stand on the board for a more comfy position?
Don't some do it? Sure, not on a fast track, but upwind?
Like wave kiters do.

Doesn't a kite pull more on 45+ degree than flying it lower? When I am totally powered, I fly the kite further down, otherwise I cannot edge anymore!

The Cabrinha 183 is based on this Aguera CR59 board, which Kent Marenkovic is riding.

there's absolutely 0 edge control. Spilling power by letting the board point towards the kite doesn't happen. Only when your going downwind and that is a SLOW process..

As for standing on the board out of the straps, without atleast one foot in the straps the kite immedately pulls you off becuase when sailing flat the board is not pushing up into your feet, your feet are pushing across the board.