Two things. 1) As stated previously, why no speed-reducing nature? 2) Do you actually use both attacking stats? Your job would be much easier if you weren't. I don't know a thing about Slowking, though, so I dunno if it can effectively go mixed or not.
EDIT: After reminding myself of exactly what Calm does, I further emphasize: do you REALLY need that perfect attack? --- FC: 0345-0681-3179 (Mienfoo, Pancham, Riolu) "corn salad is mai waifu" -NME_Enterprises
I was going to run calm instead because I felt its speed is already low enough. I'm rebreeding now for quiet. Just going to get a male with decent stats and whatever nature quiet. Breed it. --- FX 8150 @ 4.4ghz|MSI 7970 Lightning 1225/1700|MSI 990fxa-gd80|G.skill 1866mhz| W8prox64 FCs in contacts. NNID Heroxoot