Bit of a noob question here!

I want to set up SD3 to use 2 Kick drums (a la shred metal) and possibly more Toms. Can I just drag the sample from Kick 1 into say channel 9 (one of the electronic pads) and use that, or would it be more sensible to use 2 instances of SD3? Or even use the Step sequencer and track layers to achieve the same thing? What does anyone recommend?

Why not open the step writer in SD3 and write your own double kick patterns?

I decided I wanted to try using SD3 instead of buying a replacement for my obsolete BATTERY since I usually only use drum kits for demos. SD3 makes it so you are limited by certain things. If you want to put a crash where a ride is you can put a single layer one shot (or anything)but a multilayer sfz requires that you alter the sfz to allow it to work on that pad. I have a recent thread started here that the veterans explained to me how to do it. Check it out. It's not that hard to do. Or you can use dimension or another SD3 if you want and drum map it. After going through all this and previously using a more featured drum sampler, I decided next time to make my life easier ,have my cake and eat it too and buy a good drum program instead. When you start changing pads in SD3 you'll find limitations that will bug you and routing problems happen where sounds will play to a input you didn't want to because the sfz routs them that way. When I read about people not liking SD3 that much I though "Oh they are just too picky I'll make it work for me and save money" But next time I'm buying a drum program and like I said it's MUCH easier to do everything you want to. So a 2nd SD3,using dimension(for a second kick etc. only )are your easiest and fastest choices. I chose to alter a SFZ because I wanted to learn how.

2nd instance of Session Drummer would be the way to go. It will allow you to track each kick separately.