I pretty much agree with what Ellen has suggested, but I wonder, did you sail the Mistral Prodigy with a rig 7.4 m2 or larger?
Did you use the centerboard in the hired Mistral Prodigy?
How much wind do you normally get where you intend to sail this board?
A 7.4 m2 rig is really very small for the F-175, so you won't be getting the light wind performance you expect with a sail that small. 8.5-9.5 m2 free race sails would begin to tap some of the light wind potential of the F-175.
As Ellen has suggested, there are a lot of boards (Start, GO, Carve) that would be alot better for you at your skill level.
, and an appropriately sized for your wind speed you would get better performance than the F-175 with a small rig.
Hope this helps,