front discs identical to old Civic/CRX/Prelude; Porterfield
I was checking out that website with the cross-drilled rotors, and went searching for the previous Hondas that share the Insight's discs. Their part # for the Insight front right disc, listed as JBR155R, matched up with the '88-'91 CRX HF and '84-'87 CRX Si/DX. The '84-'87 Civic DX/Si shares those CRX discs of the same years.
Interestingly, they list a different part number for the Insight's left side that doesn't match up with any of these Hondas, but does match up to their part (JBR302L) # for the '84-'87 Honda Prelude Si. There was no Prelude Si in '84-'85 though.
The Porterfield R4S pads are really great, and I plan on getting them for the front and rear eventually. I have a set on my '94 Mazda MX-3, and it's only for street driving.
Although a rear disc conversion perhaps wouldn't be extremely difficult to install, the problem remains not having a brake proportioning valve that is designed for a Honda with rear discs. I have a rear disc conversion on my '84 CRX, off of an '86-'89 Acura Integra. For several months I drove around with the original CRX proportioning valve, and managed to lock up the brakes in a very hard stop. In 14 years I had never managed to lock up the brakes in that car. I changed over to the same-generation Integra brake proportioning valve, and I've not locked up the brakes since. I've read of the same issue with other 1G CRX owners. The Integra part bolts right on with no modification. Perhaps 6th or 7th generation Civic Si proportioning valves will bolt into an Insight? I believe they have rear discs. Likewise for the 3rd generation Integra or RSX. If the valves can be swapped, then the rear disc conversion makes some more sense.