We will be flying from Naples or Rome to Catania however have some issues with our luggage. We will have three suitcases from a longer trip and worry they might be too big or we will be charged fees. I haven't been able to nail down the airline we will use but all say fees and size are an issue. Does anyone have recent experience with this flight and can save me more research time by letting me know the size permitted on my airlines or what the fees might be if we have larger and heavier bags? Might they refuse to bring the bag due to size or weight? With so much other research to do this would be helpful to strike off my list. Many thanks.

Someone here will certainly do the research for you, Pudgy, have no fear. But you might also consider shipping some of your extra stuff home from Naples or Rome and thus avoiding the problem altogether.

Which airline? Their websites usually have detailed information on luggage restrictions.

As Sassafrass suggested in your other thread you could always take the overnight ferry from Naples.

Without knowing which airline you are planning on using no one can aswer your question, and as Happt Trvlr says all airlines have details of the amount of luggage you can take, and any fees involved. You do not want to be faced with paying fees at the airport, which will be astronomical, so read the website of your chosen airline carefully and book and pay for extra bags if needed.
Or ship some luggage home.

Second the idea of taking the ferry from Naples. It's a really good travel experience and would save you a lot of worry and potential expense.

There is also a train, although multiple suitcases can be a nuisance you won't be charged for them.

Where are you going after Sicily and how are you getting there?

unless you take the boat/train both ways, it's not really going to help.

I would consider whether you really need 3 suitcases - IME I need the same amount of clothes for a trip lasting 1,2, or 5 weeks; it is possible to have washing done or to find a launderette in most places. you will find travelling a lot easier if you can restrict yourself to one case each, weighing no more than 20kgs which is a common limit, except on Ryanair, when it is usually 15 kgs.

Since you don't know what flight you are taking, or which airline, how could anyone "pin down" the regulations? They vary from carrier to carrier. For one-way intra-Europe flights I suggest using Skyscanner.com and then, having made your choice, you can check the airline specifications for yourself.This question prompts a polite suggestion that you need to try harder to be more detailed in your query.
In general, short-haul flights are very precise and very strict about luggage and if you need to check in three bags it could double your ticket price. But, without specifics, that is just a (scary) guess.

If hou bring all that luggage you will most likely have to pay more to the airlines. Being less luggage, save money and it will be so much easier to get around.

Are you returning to Rome or going from Sicily directly back to Toronto or to Spain?

If you are returning to Rome, there are some luggage rental places that get very good reviews. They are about 30 euro a week. If you are going back to Rome or Naples and staying in a hotel on your return, some have luggage rooms and might keep it for you while you are in Sicily.

We have used Ryan Air a number of times with absolutely no problem. Just read the rules and follow them.