Reply by jmartel

You should be fine.

Use this calculator here: http://www.woodbin.com/calcs/sagulator/

Selecting birch, floating ends (since it’s not rigidly supported on the ends, can still pivot), and put in dimensions of 74×39x1.5 and 30lb center point load, you get a deflection of only 0.07in. You can put 100lbs before it switches to borderline.

Be careful when you are cutting it. A lot of times those blocks are held together with internal metal fasteners while the glue dries. You might chip a blade.

-- The quality of one's woodworking is directly related to the amount of flannel worn.