You never know. This 'rona might furlough me good again. I've worked one full week since March 23rd.

Anywho, good luck whenever you get to it. And don't do what I did and don't take pics.

 

+1 for pics, cause this forum needs a few rear disc conversions here and there with some progress pics in the mix.

 

**Update**
I received the 04 Si rear calipers (Summit kept pushing back the date, had to order from RockAuto) and they fit! Ordered the brembo rear discs for the jazz hybrid (260mm) and I then realized that they won't work, hit the caliper bracket. Jazz hybrid discs have a 31mm height, 04 si discs are 48mm high. The rear axle I have is from a UK jazz non-hybrid (239mm) that uses 33mm height discs. When I measure the thickness of the caliper bracket mounting area on the non-hybrid, it is 9mm thicker than the 04 si caliper bracket, which explains the issue. I've ordered the brake rotors for the 04 SI, which will be (if math serves me right) 6mm too tall to work. If I add a 5mm spacer behind the disc, then that should line everything up correctly. I'm having a bit of angst on that though, as braking systems really aren't meant to have spacers behind the rotors.

As I continue to research, I've found the bremboparts.com (set it to Great Britain for better search options) has a dimensions finder. Typing in 260mm, 9mm thickness, 42mm height (with a 2mm tolerance) I am privy to a host of things that will almost work. All this to say I am trying to decide between a few options, and I'm hoping someone knowledgeable will be able to help me out:
1) Add 5mm spacer behind 04 si rotor (not sure if I'll need new studs, 5mm seems minimal but I've never used spacers before)
2) Add washers to the 04 si caliper bracket to move the bracket to within spec of the jazz hybrid rotors
3) Use a rotor that is 10mm thick (instead of 9) that meets all the other dimensions
4) Use a rotor that is 259mm in diameter and shave the brake pads
5) Scrap the brake upgrade and just go with the stock 239mm setup (I don't have calipers for the stock size, just the brackets)

I hear you on the pics, but I'm trying to get things sorted out first. I guess I should take some pictures of progress, and as I have the axle off the car and in my living room, I can snap pics from plenty of angles.

 

I was able to get my hands on a set of calipers from a 2013 insight yesterday (need alot of work, but helps with the measurements) but just so happens to have the same part number as the jazz hybrid calipers, so thats a plus. Using my "unscientific" adjustable wrench that has mm measuring points on the side:
- 04 Si caliper bracket = 19mm wide
- 2012 Jazz caliper bracket = 24mm wide
- 2012 Insight caliper bracket = 26mm wide

Test fitted with the jazz hybrid rotors and insight bracket, and everything seems to line up well. I really want to use the Si caliper bracket as the brake pad options are limitless for those vs the other two options, but I'm not full-on racing this car, so perhaps getting some Akebono pads for the insight calipers should be all that is needed for now.