Well I know GKrellm can be set to remember its position, so why not start it without the -w (withdrawn/go-into-the-slit) option, check the remember position option is checked, and then move it to where ever you want.
Then you can leave bbpager in the slit, top left. You cant have more than one slit. Maybe request it as a feature to be added to Black/Flux box, or Wiamea or another BB fork.