Bill, as you know, I too am a "Hammond" fanatic - been playing one for 50 years (and still haven't gotten any better ). To add to what Diki was saying about the Expression pedal (yes, definitely MUST be 'long-throw'), in addition to adding those 'special' dynamics to the main organ tones, it (along with the pedal tap) is essential for those trying to get that 'Jimmy Smith/Jack McDuff/Jimmy Mcgriff' bass sound when playing this kind of 'Fatback' music. It's just a simple shuffle beat really, but with an extra dose of syncopation (aka 'groove'). It sounds best on a real Hammond (naturally) but you can come close with a high-quality clone w/pedals that you can configure like a real B3.

I threw something together to try to illustrate my point. Just straight blues changes and roughly based on a tune by my third cousin, Count Basie with the great Joe Williams on vocals - called 'Every Day I Have The Blues'. It's a little sloppy, one overdub, no corrections, no mixdown. Sounds best through bass-heavy monitors or headphones.

https://app.box.com/s/66pdsgzrb2nxjsf56vjhw7k2x8lhfnus

chas