That outside lip needs to be wide enough or wider than the recess it's supposed to seal into - right?
How could it seal in there if it's far too narrow?
Am I taking crazy pills?

 

I see Centric makes a rebuild kit with this seal that allegedly fits my 2011 LX-S Coupe.
Centric # 143.40027
Also seeing a Raybestos WK1248 kit that allegedly fits my coupe.

Anyone ever tried to install these parts successfully?

 

Called Napa back. With their part #2105 not fitting problem. Of course it's now a he said she said issue.
They claimed they didn't have a part that fit my '11 Accord. I got part # D352105 directly from Dorman's website and it specifically lists Accords 1990 - 2012 as fitting.
When given the Dorman # (from Dorman's website) Napa told me their #2105 is a direct cross part fit for the Dorman D352105.
AND YET, they claim 'by looking up my car' - now! - that #2105 does not fit my Accord - only up to model year 2009. They claim it's the wrong part and their part #1248 is the right one (and it will take one week to get it locally). Everything I see looking casually suggests the brakes are the same model in all those years and also the same in Prelude '88-01, Civic '02-'11, Integra '98-'01 Type R, RSX, TSX '04-'08 (Dorman website claim).

What a bunch of bs huh? So in a vote of no confidence (in Napa) I ordered the Centric part #143.40027 that precisely ONE reviewer said was a perfect fit. No other reviews.
I ordered it oddly thru Walmart and had it shipped to a store 50 miles from here (welcome to the Outer Cape).

So I am about to try to force in the too small part - probably tear it or remove it when it won't fit, and then reassemble it all, add fluid to replace what leaked out, and test drive it without the piston dust boot for awhile until I get around to trying to install the Centric part.

 

I got it back together. Napa Piston dust boot is still too small, and not really seated into the caliper recess. But it's pretty close and not super worry inducing. I think I may let it ride until next pad change. If the piston never really retracts until then I think the inner most part by the actual brake fluid seal should be okay.
I will clean the piston next time well, and if need be get a new aftermarket one (I saw the piston for about $20 online somewhere).

I think a useful tip here is this (get your wallet lol):
Get the outer boot lip on the piston recess. I used a few drops of brake fluid to lube the inside boot lip that goes into the caliper bore / recess.
THEN, try using a credit card or hotel guest room plastic card. That's what I did. I cut about 25% of it off lengthwise, then curled it in my hands to about the right shape, then used that to shove that boot in there hard. I mean hard, lots of pressure. That seemed to help and at least for me didn't rip the boot.

 

With it back together:

Here's my QUESTION:
The rotor / hub didn't want to turn. Then, duh, I remembered that I still had the wood block holding the brake pedal down. I removed it, but it didn't help much.
It has a fair bit of drag, it needs a fair bit of effort to turn the hub and you can hear the pad on the rotor while you a making it spin. It doesn't free spin at all.

What on earth is going on here? The piston is shiny clean. The bracket slide does slide and I re-lubed it with accumulated lube at the end of each slide pin (not ideal but only had moly LI grease and anti-seize on hand - not good ideas).
I even pried the bracket / slide out with a large screwdriver agains the main caliper body. Didn't really change either, still somewhat tight on the rotor.

And to note: With the new rotor and caliper not installed yet, the hub itself doesn't spin completely wildly free. It turns, there's some resistance which I think is probably normal. There is no grinding, gritty or wobbliness to it at all. That included with the wheel on and yanking on the wheel at north and south positions jacked up off the ground - there was no play at all, and no odd noises spinning the wheel. I assume the wheel bearing is ok.

(I had to solo stuff wood block into a fully depressed brake pedal and undo the bleed bolt about 5 -6 times. Fluid only came out after a bit.)

 

Update:
Well, putting the wheel back on and turning the hub makes a huge difference. It free spins close to the other wheels.
I've driven the car at least 1000 miles or more since the repair and the rear caliper is handling just fine.
I guess the upper slide pin was just sticking enough to hang up the pad and wear it all the way, and destroy the rotor.