Advice for First Board

I'd say I am an intermediate windsurfer who can plane in the straps and gybe off-the plane and I'm currently working on my carve gybe. I think it may be a good idea to buy my own board so that I'm practising on more consistently similar equipment, which can be a nightmare where I normally sail and rent. I tend to do most of my sailing on a reservoir where in general the wind is quite light like 10-15 knots although there can be a bit of chop depending on the wind direction. I intend to eventually start doing more on the coast where the conditions will be choppier. I weigh 72 kg. I was initially interested in getting a 125L rocket board, but I have reservations over whether or not I'll be able to plane at wind speeds toward to lower end of the 10-15 knot range. With this in mind, I started thinking of maybe a slightly lower volume freemove board, like 115L, for the width to get on the plane early and also may be more applicable to the end goal of doing most of my windsurfing on the coast. I had originally learnt on the coast in the West Indies. Any advice would be much appreciated.

Thanks!