No weight restriction in IPSC Classic other than that the 2 SS and Classic or pretty much the same Unsure of USPSA box size compared to IPSC but must fit in the box with mag inserted.
You can use a race style holster and also magnet's for magazine pouches, must all be behind the hip as is SS I believe. 10 round for minor score ( 9mm/ 38 s)
8 round for major ( .357Sig, .40, .45)
None of the silly running outside fault lines in IPSC.