Arcade stick: button mapping and hand placement

I just purchased a HORI Fighting Stick α; I had never had such a control device before. Beyond the difficulty of adjusting to the stick, about which I've watched a ton of videos already and I'm still struggling to get back jumps consistently, I have trouble figuring out how to best map the buttons.

This HORI has eight buttons, so I'll refer to the top row as buttons 1 to 4 and the lower buttons as 5 to 8.

Now, I assumed it would as easy to do the combinations with the three basic buttons as it is on a keyboard, but I was wrong: I fail to do the K+G half the time, which I have set as buttons 2 and 5 respectively (P is 1), just doing a kick instead.
I'm wondering whether I should focus on practicing the combination or take advantage of the fact this thing has eight buttons and enjoy those macros for P+G, P+K, K+G and P+K+G... but as of now I find it impossible to be in control of such a wide space with my hand, I end up playing limited to the first two columns of buttons.
And yet there's that 9 year old kid from Chile crushing people at tournaments in Street Fighter 6, so it obviously is possible to operate at least three of these columns, even a child can do it at the highest level! I'm clearly missing something, maybe it's only practice, but maybe it's something else about hand positioning.

For reference, in my PS4 gamepad I had a DoA-style setup
X - P+G
[] - G
^ - P
O - K
R1 - P+K
R2 - K+G
L1 - P+K+G
L2 - P+K+G
I was very happy with it but I don't know how to "translate" it to the stick, mainly because of my inability to reach the right-side buttons.

So how do you arcade stick virtua fighters have your buttons set up? Do you all play it OG and only use the P, K and G? How do you place your right hand?