So, with the front diff / CV axles / etc., removed from the Envoy, oil pan gasket replaced, and two new LCAs installed (previously ordered; never installed), I ordered up two outer tie rod ends for later, and took the Voy out of the garage. Finally, I was able to get the Accord in this weekend to address the rust starting in the wheel wells.
(BTW, it's nice to finally have the Envoy 'dry' underneath, and not dripping anything on my driveway / garage floor (engine oil, diff fluid, or anything else!)). No issues with 'Service 4WD' lights, etc.
Drove the Accord in, removed the rear bumper cover, and took a look at what I had. First, the D/S was way worse than the passenger. I took a 120 grit flap disk and got all the rust off of the P/S wheelwell. Then I went to work on the D/S.
Unfortunately, things were bad enough on the D/S that in two places, I had holes completely through the metal. On the worse of the two, I resigned myself to taking out the death wheel and removing a 6" strip, which allowed me to get all of the rot out behind it (which is technically the edge of the inner fender). At this point, I knew a 'proper' fix would involve welding. Off to find a body shop for a quote.
The first thing I found out is that most collision / body shops won't touch rust, unless they list 'restoration' work. So I found a local shop that did that, and went in for the expected bad news.
I explained what I had and why I wanted to fix it / keep the car (M/T, which < 3% of Accords have). He took one look at it and said... "if I do it, I'll be replacing both inner / outer quarters -- easily $5000-$6000 a side. But I'll tell you how to slow it waaay down, and you can do it yourself, which will be way more cost-effective."
I had done some research on fiberglass, but he advised against, saying it would retain moisture and eventually come out.
nstead, he recommended a combination of... POR-15 along with liquid nails to build up the now-missing inner fender areas, then more POR-15 / primer / paint.
For the two spots on the D/S that also had a couple of 'inner rust bubbles' (whatever they're called; see pics), he advised removing the gas filler surround and spraying CrMo chain lube in the area.
As far as paint / blending... he didn't want that part of the job, either, and advised me to keep it to a minimum, as the farther up I went with the paint, the worse it would look (e.g.; I'd never be able to get it to 'factory').
So... the good news... I should be able to get the (current) rust on the Accord mostly removed, cheaply (along with a bunch of time on my end, which is fine.)
The bad news... it makes no sense to try and remediate the rust issues the 'right' way. So I've got a relatively low-mileage (145K) Accord with a 5MT that will likely succumb to rust before I get the remaining miles out of it (easily another 150K, and that's probably 10 years away or more, for me). To say I'm sad over this is an understatement. If the rust were on replaceable panels like hood / fender / doors, I'd just replace the panels outright. But it's on the rear wheelwells.
Thinking about fixing it up as advised, then selling before the rust gets worse, and finding another M/T-equipped Accord (they're available until 2018 MY, but rare as hen's teeth). And I like the '08-'12 model interiors better than the '13-'16, as well.
Oh well... "1st world problems", as they say.
I know some of you have worked with fiberglass, although more on the interior (like for building sub enclosures / dash panels), vs exterior / body, based on my search results on the site.
What say you?
I've watched a couple of YT vids on how to do it, and while it's a lot of work, I'll do it if it'll last longer. I'd like to get at least 5yrs out of whatever method I try. But I know I won't be able to blend the paint, and that part will look like ass, which I don't want.
PS: If someone wants to see my upcoming work on this as a separate 'generic' body / paint thread, let me know. But I'm guessing no one wants a half-assed repair method documented.
PPS: Yes, I now have a welder. But I'm not about to 'go learning' on the Accord.
Pics below:
(note: What's left here is a rubber strip. In the middle is the remainder of a spot weld (which I'll grind down)
This should be much less labor intensive than replacing that damn spring though, so there's that.
That wall mounted one looks nice. That got added to the wish list for future dreaming. 
so we're going for brunch at my aunt's, then shopping at a flea market and then back for dinner at the aunt's. Tomorrow is bug out day, of course, when the weather turns nice 
Pulled the release cord and messed with it for a bit, not fully realizing what my situation was until it was too late.
. Then replaced one of the 110V receptacles in the phone charging station with one that has four USB charging ports. With most charging bricks and the cable, I couldn't close the door. Then finished up the back wall repair by re-taping the roof.
