Welcome to the forum
No. You can buy a second module (I use a td6v) or a TMC-6 to do this.
1) Can I wire up additional drums via a ¼” Midi patch bay?
Yes, of course. No problems.
2) Has anyone tried using a Double Kick pedal with the KD-8?
I would look to replace all the pd8s eventually, your wrists will thank you. If you can figure out how to suspend the pd8, you can probably use it as a kick trigger - other people have used mesh pads as ersatz kick triggers. Would this be instead of the kd8 double kick or in addition to???
3) And finally, the kit came with three PD-8’s. I would eventually like to buy two larger floor toms and only use 2 (of the 3) PD-8’s. Does anyone know if I could use the extra PD-8 as a Kick trigger?
TD9+6v module, KD-8, custom Diamond Electronic 12" snare + 2x8" + 2x10" toms, PD-85, 4xPD8, 2xCY8, CY-5, CY-12r/c, Pearl P902 double pedals, Diamond Electronic COWBELL!
HPD-10 ATH-50M phones and 4 Vex Packs for the TD-9
Gibson Les Paul. + pod xtl, Norman acoustic, Fender J-Bass + gt10b
Clavia Nord Stage 2 Synth/Stage Piano Samson SR850 'phones
cubase, garritan personal orchestra, JABB, symphonic choirs, Sibelius, reason 6.5, IPAD 2 with lots of soft synths...
three shelter cats