I really hesitated to join this conversation. I could debate these types of things all day, but I greatly dislike presenting points without some type of data to support them, and I certainly don't have time right now to dig up statistics. But, before trashing my message I decided to post with the disclaimer that these are my thoughts based on past experience, and I cannot provide links to support them, etc. But, these are my thoughts. Big business loves big government. Monsanto is powerful. It would be a miracle if the free market system actually applied to Monsanto. With government regulations and agencies on their side because of power, millions donated to politicians, it doesn't matter what the average joe or the struggling farmer thinks. Monsanto can call the shots. They purchase smaller competitors to get rid of competition, and they have plenty of hands in Washington, DC, supporting them. They, and other big corporations like them, do it partly in the name of the "public good." I am reminded of the wonderful legislation that made it illegal to sell toys unless they had had extensive lead testing. Didn't matter how very rarely lead is found in toys. Mattel was a big proponent of this legislation. Why? Why would they support legislation that adds money to their total cost, drives up the price of their toys to consumers, and basically addresses a non-problem? Now it's illegal for thrift shops to sell second-hand toys unless they've been tested. Mattel just eliminated a huge industry that competed with them. I know of small publishers that had to trash their entire CD/DVD industry because they couldn't afford lead testing on their already-printed products. Some went out of business. When do babies chew on CD/DVD's enough to justify regulation? Some states have even said they are going to police/monitor garage sales to be sure no untested toys are sold at garage sales. Big $$ for Mattel if you can only legally buy new toys. Same goes for Monsanto. I believe only in the free market, and I believe government manages to cause everything in which it is involved to decline. Monsanto isn't truly operating in an only-free-market system. Politically I am a strong conservative. I used to champion private companies. Now in my old age I am seeing how large corporations are able to manipulate markets through their connections in government. I am greatly disturbed. Monsanto could do with some good competition, but it's hard to compete with a corporation so big they can control the people who make the rules. It would also be a breath of fresh air if states would begin fighting/nullifying federal agricultural regulations that hurt their farmers but increase the market share of Monsanto and other ag companies like them. We as people have such a smaller voice in Washington, but sometimes our local reps listen to us.

When you pay for the reproducible plans, you have the right to use them to build one house. There's no reason the house has to be built exactly according to the plans you bought. In fact, it's no doubt the usual case that stock plans get modified to some extent during the building of the house. One reason is that stock plans don't take local codes into account, and these codes may affect things like window size and placement. And most people will want to tweak the stock plans to suit their individual circumstances. There's no reason you have to hire Don Gardiner Inc to make these modifications UNLESS that's what you specifically agree to do when you buy the plans. So you might want to check into this just to make sure. But I believe most stock plan sites just offer in-house modification as an option, not a requirement. An experienced GC should be able to make the type of modifications you describe.

Go with your original plan ... unmodified underneath and modified over. Ease of removal is not the reason. Using a dry-set (unmodified) type allows the wood subfloor to react more independently, and not transfer slight lateral movements up thru the CBU. It provides full solid support to the CBU without making a complete bond like a modified type is made to do. I know this does not make a whole lot of sense, but the TCA performed many tests on this.

The polymer additive is only an extra that most use for stuff that will be outside. It tends to make the mortar more flexible. You can use plain mortar mix, Quickrete brand is what I use. The Mapai brand is nice to use, but not necessary and don't lose any sleep over it. The Quikrete brand is what brick layers use, and is quite a bit less expensive than the Mapai. When and if you can get the Mapai brand, Slow and I use it and the Mapai grout almost exclusively. I am using the less expensive mortar on my column because I have to use a lot of it. Hope this helps.