Hi Rory,
Great to hear you're diving deeper into whipmaking—especially moving toward an Indy-style whip!
Regarding the foundation for the palm knot (not the transition knot), you're right—there's a bit of artistry and variation involved. Typically, the base is built up using shaped leather or cord—sometimes layered artificial sinew, waxed thread, or even thin leather discs that taper slightly to create the domed effect. Some whipmakers also use epoxy putty to sculpt a durable base under the knot.
The strand thickness used to cover this area usually matches your overlay strands, but if you're using a finer kangaroo lace (say 2–3mm wide and around 0.6–0.8mm thick), you may want to cut them slightly thinner for the knot itself to reduce bulk. As for the bights, an 8- or 10-bight turk's head is common, but you can go more intricate if you're aiming for a classic Indy aesthetic. Many Indy-style whips use a 3-pass 7×6 or 7×8 turk’s head.
About the handle shape—yes, you’re spot-on again. That gradual swell near the thong transition is intentional. It adds grip comfort and helps with the whip’s balance and handling. This area can be built up with leather or cord wraps under the plaited overlay, and gradually sanded or shaped to get that swell.
Keep plaiting and enjoy the journey—every whip gets better!