all good advise but me being in florida we deal with this all day long , yes do a test first ,that is a must , and do this on the substrate, lol, a true reading will take a few days , second the use of vinyl, well helps but not sure fire , a good sealer is what is best ,and not some product from them big chains ,they do not and never will work ,being that high you need the right products , this is common sense to most of us in this field, a sealer that works and proven is worth its wieght in gold , and i do agree with the use of a company that is not some big chain, they just do not have what it takes to know what is best for you the customer, we are in the field everyday ,and we learn or hope we do everyday and take pride in this , sorry but most of the time the big chians more offten then not are more costly in product and call backs , your local woodman can most of the time beat the price of materials and give you a better all around end product, good luck

The best installers I've run into do not work for "box stores".. they sub-contract for the "better dealers" and work directly for consumers.
Good installers, like small "mom and pop" retailers, depend on happy customers to make a living.

There is no such thing as a "SALE" on installation.....

No such thing as a "Good Deal" on installation.