I must tell you a bit more about your stringer system and CCA Pressure Treated Plywood.
During the late 1970s Ebko used marine plywood to manufacture their boats. This was an accepted, although poor method to build the floor and stringer systems. In areas Ebko would double the 3/4 plywood stringer/grid system and fiberglassed it in place. The stringer was not always fully encapsulated, which allowed moisture to penetrate the plywood quite a bit quicker than the screw and/or staple penetrated areas. A Ύ CCA Pressure Treated Plywood floor is sufficient if it is fiberglassed coated and tabbed in place!
A floor, 1 7/8 thick will add a significant amount of weight and is simple not needed. AWPA Standards for CCA Pressure Treated Plywood: Salt Water (Pilings, bulkheads, etc.) contact is 2.5 lbs per cubic foot, above ground (Decking, fences, etc.) is 0.25 lbs per cubic foot. (Note this is for pine, Fir, which is better, is a bit heavier) CCA pressure treated wood is available in a variety of retentions for various applications. Preservative retentions are in pounds of preservative per cubic foot of wood as per the American Wood Preservers' Association. Assuming you are talking about the pounds per cubic foot, or one sheet 4'x8'x3/8" sheet of plywood (which is one cubic foot); the weight would be approximately 36 pounds. You figure it out. Depending on which model you have it only weighted between 2600 pounds and 3000 pounds new.
Crownline Boats, which build an excellent product, web-site, http://crownlineboats.com/aboutcrownline/tour/tour5.php
, illustrates an excellent stringer system built with Ύ CCA Pressure Treated Plywood. I have built many thousands of family runabouts with a similar system using CCA Pressure Treated Plywood and never had a single failure.
Unless the CCA Pressure Treated Plywood is left outside, the comment about PT being quite wet is simple not factual. Most Mills that manufacture CCA Pressure Treat Plywood kiln dry it. To my knowledge all CCA Pressure Treated Plywood is kiln dried to equalize moisture content. By equalizing the moisture content with the atmosphere, the plywood resists splitting and cracking. Every piece of plywood is dried to nearly exactly the same moisture content, every time. Kiln drying helps eliminates shrinkage, twisting and warping.
One of the most effective wood preservatives available is chromated-copper-arsenate (CCA). CCA Pressure Treated Wood is lumber or plywood that has been impregnated under high pressure with preservatives that protect the wood from termites and fungal decay.
What makes CCA so effective is that wood treated with this preservative will literally last for decades even in harsh outdoor exposures. Independent tests conducted by the United States Department of Agriculture (USDA) confirm this: wood stakes treated with Osmose CCA preservative remained resistant to termite and decay damage for over 60 years. That's an anticipated life of 5 to 10 time