FX Impact mk2 side shot mags - Issues?

Was looking at the mk2 sideshot magazine , it's high capacity 28 rounds in 25 cal. plastic. I read it will struggle with heavy pellets / slugs? Does this mean 34g pellets will not cycle effectively? Was also mentioned in post about year ago that only short slugs would work. Otherwise use the original sideshot high capacity mag made from aluminum for the MK1 Impact. Comments?
 
Was looking at the mk2 sideshot magazine , it's high capacity 28 rounds in 25 cal. plastic. I read it will struggle with heavy pellets / slugs? Does this mean 34g pellets will not cycle effectively? Was also mentioned in post about year ago that only short slugs would work. Otherwise use the original sideshot high capacity mag made from aluminum for the MK1 Impact. Comments?

I'll say give it a try, it might work on the ammo you are using, and if not you can get one of the inserts Elis mentioned.

When Steve was here with me we were using his impact with the MKII and the original magazine with no problems at all.