If the fermentation is stuck and you get stuck with a weak beer......Add a .5 gallon bottle of Coconut Rum to it before you bottle it then let it condition for @2 or 3 months. If you use 90 proof then that is 45% and 4.5% boost in Alcohol by volume of 5 gallons. 1 liter of 90 proof will raise the beer alcohol by 2.6% which would give you a average alcohol level.
I did it to a Brown Ale that stalled out on me. It was a wonderful beer once it mellowed. Expensive but worth it!