I find when having people handle snakes it's the individual's comfort ability that determines if they can handle it or not. The size/ type of snake doesn't really matter until you get into the ones so big am individual shouldn't handle them by themselves. If you think you are gonna be uncomfortable handling it then most likely you will be. If you think you will be ok or could become ok with it them you will be.

Even if the snake is larger then the average boa like you say, if you can handle holding 20 lbs ish you will be fine. If that is too much weight for you then you shouldn't get it. You say it's fat like a blood. Average blood adults are around that. A little less even. Even the really large ones usually don't get above 40lbs(but it has happened). Snakes can look a lot heavier them they actually are. If you don't think you can handle a weight like that. Get something else. If you are able to handle something that size you'll be fine. I have seen kids around the age of 10 handle and extremely large red tail. They couldn't do it for a long time but they still did it.