More sugar
I did some research on Port wines. Most are 20% alcohol, and 10% sugar (100 g/L).
Ours is 19.4 % alcohol, and ~6.2% sugar (62 g/L).
I have been topping with syrah, and once with Diesel to replenish the alcohol.
I will do a sugar addition. I think getting to 8% first is a goal, and then have it tested again.
That is an addition of 2%, or 20 g/L. The barrel is a 50l barrel, so need 50 * 20 = 1000 g!
The next “topping” will be with table sugar, and a lot of it!