Cumaru has moderate movement. Not a lot but definitely some. If you have humidifiers/dehumidifers/ac to keep a consisten temperature/humidity through the year that's a good thing. I mentioned this to floorguy before but got no response. Not sure if he is confusing brazilian teak with real teak (tectonis grandis). There is a large disucssion with legal harvestation of real teak - with the sustainable teak being "plantation teak". The best teak(true teak) in the world is from burma. Unfortunately burma and the us don't get along (sort of like cuba) - therefore anything from burma is labeled 'illegal'. Now, not getting into whether its forested correctly or whether the political powers that be in burma are right/wrong but the rest of the world use burmese teak - just not us. We'll use a lot of other woods that are harvested in much worse conditions than burmese teak but because us nd burma are politically at odds - burmese teak is 'illegal'. Brazilian teak is harvested similarly to brazilian cherry - and its whole issues in the brazilian/south american rain forest. they are two distinct woods with the "teak" common name (brazilian teak is not teak, just a common name for us to associate it with a desirable wood that isn't as widely available).

We had unfinished Brazilian teak floor installed in a kitchen/dining room remodel in 2012. We have had no problems of any gaping and absolutely love it. Also, the installation was a breeze for the contractor who is our son-in-law. In 2017 we remodeled the master bedroom suite with walk-in closet and again installed Brazilian teak. Flooring material was purchase from the same dealer and installed by the same contractor on both projects. The wood had more than 7 months in the room it was to be installed in to acclimate to the indoor environment. Our son-in-law had a lot of problems with the installation on the bedroom project. Installing the flooring took more man hours and we are convinced that the second batch of wood came from a different supplier. It seemed to be a lower quantity even though we were told that it came from the same supplier. There are some gaps but after having the salesman we dealt with inspect the flooring he had them filled before his finisher completed his work. We absolutely love the floor in both areas and wouldn’t hesitate to use the same material if we were to ever move.

Lots of wood is as hard as teak and it can be difficult to work with. I would not put down plastic - I use felt (tarpaper) and it works well. You can use any gun that will get the nail thru - just adjust the setting right and try a few shots before you put the floor in. I use an old fashioned kind of thing where you just pound it hard with a mallet - works well enough on Brazillian cherry, bloodwood, mesquite, and various other woods that are also hard. You pre-drill the first planks and use a flooring nail to secure, after which you can use the gun. You bought pre-finished flooring, so if you have never done this, take a couple of the warped pieces that you are going to have to scrap anyway and use them for experimenting. Nail a couple to the middle of the floor where you can easily rip them out. See what kind of difficulty you may have. And if you are going to nail thru the tongue, definitely pre-drill and then slightly ream the hole and then use a nail set to make sure that the nail head sinks properly, otherwise you will have a gap. If you do not do this, you can split off the tongue. Try one of your sample boards w and w/out pre-drilling to understand what I mean. Always make your mistakes where they won't hurt you later. One problem w some of the hardwoods is that they can split and splinter more easily than you might think, so be aware of that or your hands can get shredded. Also, get a good new saw blade. Where you cut the boards, you do not want any chipping, so slow and accurate is the rule and you get nicer edges. Also, don't expect everything to be a perfect 90 degree cut, even on the boards you buy. I have never found the edges to be perfect. Since I'm a little fanatical, I make them perfect. Make sure you have a good router too - you may want to route the ends. Some people don't but I do where they lock into the border, unless you are not putting in a border and then you can simply run them into the wall. Good luck.

Cumaru is also known as Brazilian Teak. You will find alot of info under that. Good luck!