Our keys to provisioning for long cruises.
1. Have a long and detailed list of all items used on the boat. Otherwise, you overlook something small but really needed. You run out of salt or short on shampoo or find you have no Neosporin along the way. Don't overlook medical and first aid items.
2. Determine storage requirements for the various items, type of storage needed that is, and the ability to replenish along the way.
3. Minimize the space requirements of each item needed.
We vacuum seal all meats. Outside of fish we don't depend on purchasing meats anywhere out of the country. Meats are the freezer number one priority. Once beyond meats then you see what space for vegetables. I know the mention of canned vegetables brings many severe pain, but if all your frozen vegetables won't fit, then canned is the only choice.
Don't overlook any storage possibilities. The spaces least used and often overlooked are the key spaces for long cruises.
Figure out what items are available on the cruise and where and at what prices. You may even find it makes sense to fly certain items in, even though cost penalties to it.
For food, do menu planning, complete menus. Make sure you look at all meals. However, also recognize that whether you or others catch them, fresh fish can be found along the way and that you will eat out some. At first, that's one of the hardest things to judge, how many times will we actually eat on the boat.
Don't overlook snacks. Find snacks that can survive than length of time. Three months is a long time for many snack items.
Evaluate things that are especially space hogs. A huge one for us is ice cream. We can't take a gallon of every flavor we like. I can get about 10 vacuum sealed steaks in the freezer space, one half gallon of ice cream takes.
Don't overlook leftovers. Keep in mind that some of the "meals" will actually suffice for two meals or more, that when you cook this roast today, that takes care of 4 meals in total.
As posted on the OP's blog, no cardboard. Nothing that requires extra space.
Keep a list of what you take and where you put it all. Nothing worse than "I know I bought it and put it somewhere, but have no idea where it is." Cans of food fit in places that nothing else you have will fit, places not really good for normal storage. We use tons of suntan lotion. The tubes will fit most anywhere imaginable. We do put them in plastic storage bags though as accidents can be messy.
Use trays and plastic containers and other storage devices. Amazing how much will fit under a bathroom sink if it's packed several levels and fixed to prevent any of it rolling around.
Ultimately most boats have far more storage space than we think. The only issues we've ever had were with storage of perishables. Freezer space is the real issue.
Fresh stuff usually gets delivered weekly. Staniel Cay and Georgetown are pretty good with multiple choices. We tend to bring the comfort foods, frozen meat/chicken, beer/wine and toiletries. We don't really do cans at home and haven't found we've had to in the Bahamas. We've found our diet does change but it's all good. Remember, don't have too much fun. 
