Your first step in planning the addition of a swim platform will be to obtain a wood locating diagram for a 2001 DAUNTLESS 16 from Boston Whaler customer service.
Once you have the location of embedded wood reinforcements in the transom of a 2001 DAUNTLESS 16, you can begin to design the platform and its support, and where the support will attach to the hull.
Attaching of a structural bracket that can support the weight of an adult human standing on the platform must be done with very secure fastening.
The best possible method will be through-bolting of the frame to the hull. You must determine if this is possible by assessing the shape and thickness of the hull at the chosen point of attachment.
The next best method of attaching the support frame to the transom will be to use appropriately sized screw fasteners that tap into the embedded wood reinforcement in the Uibond hull.
Typically the support for the swim platform includes an overhead frame member that acts as a hand-hold for the swimmer who will be coming up the ladder and pulling himself onto the platform.
Typically there will also be a frame member below the swim platform that will be in compression, and terminating with a strong attachment into the transom, but with the force acting on the fastener as mostly a shear force, not a force attempting to pull the fastener out of its attachment to the hull.
I recommend you look at Boston Whaler OEM swim platforms stainless steel tubular frames to see how they are built before undertaking the design and construction of your own swim platform support frame. You can find many images of Boston Whaler swim platforms using a search for images and the search arguments "Boston Whaler swim platform".
For example, visit the GOOGLE search engine, and use this argument for the search
swim platform site:continuouswave.com/
Then select the IMAGE tab. You will see several images showing swim platforms on the transom of Boston Whaler boats.
Fig. 1. An image showing the swim platform on an OUTRAGE 18 transom, located with the search method mentioned above. The support from the platform that extends upward and attaches to the transom is very likely through-bolted, as the transom thickness at that point is not so great as to be prohibitive of through-bolting.Also, there are many off-the-shelf swim platforms with integrated ladders available that would be suitable for use on a 16-foot boat transom. I do not see there is a compelling reason to fabricate your own welded stainless steel support frame, but, of course, that approach may be a good option for you due to your skill at creating welded stainless steel tubing frames.