Hey Pondoro, I made mine with 3/4" poplar but I wish I had gone 1\2" due to the weight the 3/4" added. It does sound fuller and more boom then the factory built one I have but just not as mobile. Yours looks great. You did a good job. It took me about 3 weeks unsure of the hours spent to build 2 of them. I bought snare wires for a snare drum and cut it in half and put them against the faceplate of each one to give it that snare sound when hit near the top.
Makr1 - The weight doesn't bother me, my first cajon gets used for a chair, table, music stand, etc. The second one is going to sit in a common area at my daughter's college residence, so it will take a similar beating. I want them sturdy. Oh yeah, they are also used as drums!