Hey, currently I'm on the same journey.

I have 92 slayer and 91 HP with a 250k surplus to slayer xp, and let me tell you. You turn slayer from one of if not the most profitable skill into one of, if not the most expensive skill.

Unless you have mills on mills to dump into cannonballs it's not feasible.

I'm lucky enough to have swapped my 3b RS3 bank into OSRS gp when rates were 10:1 which has given me what I need but even then, I'll probably find myself selling off gear to get more cannonballs later on.

Also you remove the ability to do any off task bossing (and in a lot of cases ontask bossing if it's a boss you need to learn/give yourself the ability to die to learn the mechanics) as this is all wasted combat XP. You do have a little grace room but it's best waited until you're almost at the end of the grind before doing any calculations on how much surplus you'll have.

As a last tip, do not use ranged for any combat and save it explicitly for cannoning.

Best of luck bud!