I went through a similar experience when i moved from the long board to the short boards with centerboard. I found that sinking the leeward rail was a very big factor.
The longboard roles over without any effort on your part so it doesn't require a special technique. The wide boards like the Rio almost refuse to dip to leeward. this is a fantastic feature for stability so you never fall off but it means that you tend to have more trouble with upwind progress. The other nice thing about that is that it makes it much easier to carry a much larger sail so you can get planing sooner in the light wind.
So you need to everything you can to sink the leeward rail. The more length and thickness of rail you can get under water the better it will go upwind in displacement mode (centerboard down).
Secondly, for more planing time or speed in displacement, look at bigger sails if the budget will allow. I now mostly use a 10.5 or minimum 8.5m while on the old longboard I used to find 6m hard to handle.