Hackers Help: Kitchen table and bench! (need help!)

Hello,

So I just got an apartment and I am about to build half loft bed utilizing Kallax (I will post pics)

Since I am already making a large order from ikea I thought why not make a table? My apt Kitchen is fairly small and more of rectangle. I have a large area that is unused.

My goal is to have a table I can use to prepare food as I love to cook (and do not have enough prep room right now). As it is small area I feel that chairs are rather impractical. Not to mention I love benches!!!

So my idea is to have a table at counter height or bar height. For the table I am going to use the Numerar 73×26 counter. I am thinking of setting it on two Finnvard trestles.

For benches I am thinking of using Kallax units (with MDF and foam on top).

The measurements work perfectly for the space however I have two questions!

 

1. how high does the Finnvard trestle go on its own? I have seen extensions for standing desks, but I am curious how high it is on its own I cannot seem to find that measurement.

2. Can I build a bench out of the Kallax units? I have seen ones out Expedit single units. I want to use a Kallax double unit however. Would these need extra support? Does having it twice as high make it less able to bear weight?