Need help with creating support structure for steel tub
Hey guys, I kind of have a unique question. I recently undertook installing a new tub in my home. It is a lot of work and have ran into some minor issues. I have one more issue to deal with now though...
I had called the manufacturer of the tub I am going to install to ask them weight specs. The user of this tub is 425 pounds and so I needed to ask the manufacturer if the foam pad under the tub was sufficient for support. They said the tub is only tested up to 300 lbs and is not recommended above that. I'm assuming all steel tubs are probably around the same weight load limit. Cast iron is currently out of the question due to its weight and difficulty getting it into the place, not to mention I already have done so much work on this steel tub and the bathroom according to its specs, so I do not want to return it the steel tub.
I really don't want to void the warranty and remove the pad just to lay a bed of mortar, but I do want extra support since the tub is not meant to hold a 425 pound man, it is meant for only 300 pounds or less. Do you think it would be okay if I did this: Cutting wood from 2x4s and shaping it to fit the base of the outer edge of the tub and creating a rectangular shaped structure to go around the foam pad on all sides (that way I can keep the pad). I would cut the wood so that there would be a gap between it and the tub, and in that gap I would pack it with some foam padding I bought from Lowes to allow the tub some "give" with weight and to soften the way the wood feels to the tub. I attached two pics to show you what I mean. The first one is of the tub's foam pad, the second one explains more of what I want to do.
I don't think steel really cracks, but I know it can bend, which is why I want to install additional reinforcement.
So what do you think? Is my plan for extra reinforcement using wood and foam padding good and safe? Is there anything wrong with my structural plan?