I ride ovals (absolute black) on my MTB, and gravel bikes. Love them, and are faster with them, but with that being said, How do you plan to adjust the indexing? All the current ovals that are fixed, are designed for diamond frame bikes, and are indexed for the leg/chain angle, which, if you look at a side view, the average angle is close to 90 degrees to the chain line. The oval chainrings are indexed for that relationship. On standard recumbents, (which I used to ride before Cruzbike), that angle is much lower, as you are leaning back, and are getting close to being parallel to the chainline, so, the oval will not be in the correct indexed position. I ride a V20C, so that angle is not quite that close to being “parallel” to the chain line, but still out of index for proper power delivery.
I know Rotor makes indexable ovals, but I don’t think there is enough adjustment to account for that leg/chainline relationship.
Back in the 80’s, I tried Shimano’s “Biopace” ovals, and they had it exactly backwards, where the high point of the oval was in the difficult portion of the pedal stroke, and the small point was in the position where you had the most power to put down…
Exactly opposite of the modern ovals.
I did not go with an oval on the V20 for the reasons stated above.