A kitset can not be set up containing a product with a serial number.
Checking that warranty a would be set up correctly when a kitset – consisting of a ride on mower and a deck was sold.
The deck has no warranty or status as a Customer Item, but the ride on mower does.
The only option in that case is to sell the combined item (ride on mower and deck) as a build up. /B on the invoice line.
When that is done the Ride on is correctly set up as an Custom Item and has the warranty assigned to it.