I have one FHX-1 expander for my expert sleepers FH-2 midi interface dedicated to LFOs. So that's giving me 8 (clock synced) LFOs in 4HP. Could easily add a few more. The only potential issue being that those LFOs have to be configured on either the FH-2's tiny screen or via Midi CC on something like a Faderfox or (in my case) an Octatrack. I wouldn't recommend an FH-2 just for the LFOs :) But if Midi is something you need in your rack anyway... why not? Works for me.