modding qanba q1 questions

Hi, this qanba q1 is my 1st arcade stick and I want to change the default buttons.
I know that modding qanba q1 is easy if I choose sanwa buttons, however I had in mind to use concave buttons because the arcade machines that I played when I was young were using concave buttons, pretty much every single arcade in my area had those buttons and I love them.
If I choose concave buttons, are they easy to fit in my qanba q1? because watching the video bellow, seems that maybe If I want concave buttons, those buttons does not fit in the holes as sanwa buttons fits, and I just want to do the same that the guy of the video do.
Also one more question, about those concave buttons, I read that the classic ones are "happ" buttons, however Im looking few shops and seems that they dont mention happ anywhere, I saw some with a different mark or just called "third party", they all looks the same buttons anyway, need I to research "happ" buttons only?. Well that would be in case that I decide to choose concave buttons, I need to know if those buttons fits ok. Thank you and sorry my english. I did my best :)