If you use such tool as describe above, be aware..
Bamboo has convex back, so, when put backside down to plane with this tool, the whole back does not make contact with ground.
In this case, the bamboo wants to flatten itself and this can cause it to split when it starts to get thinner than 4 mm.
What I do, is I look at end of bamboo and check the crown. From the top of crown down, I measure how thick I want to finish it.
Lets say 3 mm, measure down 3 mm from the crown and then mark line horizontally. the line will not be able to extend full width because of crown. Mark down again from where it runs out and down to belly. Do this to both side. This mark width of your backing. Usually, around 3~4 mm think I can get 1 1/4~1 1/2" wide backing depending how convex it is.
Cut to width lines you have drawn, make sure it is very uniform width! Next, plane/remove material until you reach edge of crown. At this point, there should be an edge on whole length. You will have perfect thickness whole way even if the bamboo isn't straight.
However, this only works if entire backing will be made as one thickness whole way.