I want to know how what program change commands to use to change kits, they don't seem to be documented anywhere ..
You send standard MIDI bank select and standard MIDI program change messages to switch sounds in real-time by MIDI, like you do with any other standard MIDI software or hardware sound module. Which bank numbers and which program numbers exactly depend on you, since you have to define which one of your sounds should react on program changes at all, which bank & program numbers they should be assigned to, and which memory loading strategy they individually should use ("on demand", "on demand hold", or "persistent"). So with the loading strategy you can define whether i.e. some certain sound should be kept loaded in memory all the time, i.e. to enforce immediate sound switches without any delay, or you can just let some load if really needed and freed once not needed anymore.
Here is some overview about the sampler's so called "MIDI instrument mapping" feature in general:
http://www.linuxsampler.org/api/draft-l ... %20Mapping
I recommend you to use Fantasia/JSampler to setup the MIDI instrument mapping, that should be fairly easy. The document above is just meant if you need some more background information about this feature.
BTW, by default the MIDI instrument mapping applies to all sampler parts equally. If you rather want to have the behavior of many standard MIDI devices, that is having MIDI channel 10 assigned to drumkits only, and all other MIDI channels to regular instruments, then you can also do this by creating two separate MIDI instrument maps, and assign the sampler part of MIDI channel 10 to that separate 2nd MIDI instrument map.
I am using SFZ ..
Then just adjust your SFZ file to trigger notes on the respective MIDI CCs you need.
I think 5 days is a little more than a few hours ..
Well, you were complaining after 49 hours for not receiving a reply to you questions. Like I told you, it is normal that you may have to wait several days or even much longer to get a response on this board. One reason is that most developers don't lurk on this forum every day, that's why I suggested you to subscribe to the developer's mailing list in case you are unhappy about the response time, and the other big reason about the lag in responses here is that 99% of all users just pass by on this forum to ask people to get their issues resolved as conveniently and quickly as possible for them, and then never ever pass by on this forum again to help other users.
But I am sure that you are different and will also help out other users on this board in future in less than 2 days.