Yea Iíve not had any issues running unmodified Tapco 20s although they didnít feed stripper clips as smoothly as the fixed 10. I went back to the fixed 10, best option for bench shooting. And I didnít like having to lock the bolt open if you wanted to swap mags before you shoot the last round.
I put a fixed 20 on my first SKS back in the 90s when they were cheap and it worked great, but theyíre pricey these days. At least Tapcos are cheap.
If the Asian drums run as poorly as my Asian 10 round mag Iíd pass.