We're attending a wedding (formal - read spiffy suit for Dad and mother of the groom dress for me) in Rome and then are going to among other places Venice. So no, you can't cram wedding clothes into a backpack. That said my hard sided suitcase, packed, weighs in at o/a 35 lb and is easily for me to lift. Any problems taking it on a vaporetto. We're staying for a week so storing our suitcase at the train station isn't really sensible. Oh, and yes, we VERY much like the soon to be bride.
There are ALWAYS pieces of luggage everywhere on the vaporettos...seems somebody is ALWAYS traveling :-)
As far as I know you just walk right on the vaporetto with your suitcase. We saw people bringing all kinds of things on board. There is no luggage storage, so just keep it right next to you. We took evening clothes (dress suit for him, evening dress for me) to Italy last summer as we had tickets for a performance at La Scala our last night. We each packed our outfit in a large size Eagle Creek packing envelope, carefully folded. That went at the bottom of our roller bag (carryon size) and stayed undisturbed until the end of the trip and our fancy night out. Mr dress was fine but he wanted the fold creases out of the suit so he took it to a dry cleaner across from our hotel. They presses it for him for ten euro.
Usually there is a storage area right where you enter the vaporetto, a sort of platform/box right behind the wheelhouse. You may see people leaning on it, but if it is not already filled to capacity, it's a good place to squeeze in your larger item.
Try to avoid the traditional "rush hour" times. (We usually try to arrive in the evening and leave early in the morning) Of course, you may not have choice of when you arrive, but if you do.... it will be much easier.
It'll be much easier on one of the large white vaporetti which ply the number 1 route than if you grab one of the black motorscafi on some of the other routes. The motoscafi have more steps and are much narrower. The storage area on the vaporetto is the answer I had also thought of.
If you are wearing a backpack, just remember to remove it and place it in front of you. You will see signs on the vaporetto reminding you to do this.
Ditto the above, esp. the Packing Envelope (love 'em! keeps your clothing from moving around and getting wrinkled no matter how compressed they get) and avoiding the rush hour boats (although it's Venice...probably morning and evening are less crowded than the middle times LOL) Congrats on the new D-i-L! A few years ago, I traveled with my M-i-L for 10 days in Europe - just the 2 of us. We each got the strangest reactions when we'd tell people our plans to travel together, just the 2 of us! And we're going back this fall, although her son (wink) is coming along this time...;-)
Marie, No problem. You can bring as much as you can carry. Edwin
Having traveled with family to Venice who don't quit yet understand what it is to pack lightly ... yes ... you can most definitely take ginormous pieces of luggage on ... and you can make the poor men in your party carry it :( ........