Looking at the figure given in the instruction book.
It is basic but will work, no problem. Remember simple is often best. It is also worth remembering that sail boats generally have a balanced design to give good performance. Once you start shifting things about you could be making the boat sub optimal. Below I explain what I mean by shifting things about.
From the diagram you are looking at having the gooseneck 19mm off the base of the mast, I am also assuming this would be the deck.
This leaves no room for an additional kicking strap.
If you make space for a kicking strap (non essential) then there will be two knock on effects.
Firstly the gap between the deck and the foot of the sail will be increased, quiet a lot proportionally, and this will have a negative effect on sailing ability. The smaller the gap the better.
Secondly, you may need to recut the sail, cutting off the foot. Or lengthen the mast. The former would give you a smaller sail area and shift the centre of effort forwards, she would not sail so well. The latter would put more weight up high, and the centre of effort of the sail would also be higher. This would affect how far she tips over in the wind. This in turn means you cannot sail in as strong a wind as before.
We are only talking about 2cm, but on a smaller vessel 2cm may not be negligible. As you said, you won't be racing. So why spend additional money on custom parts? Keep the cash for beer.