Going to be a bit tough. Waders and boots are bulky, especially for two. I use the passenger seat, trunk and both side cases just for me when camping, but, I like my comforts (like a 4 person tent and inflatable bed, not air mattress).
But, if you really went to the minimums then you might be able to get by. Probably have stuff strapped on everywhere
If you have not purchased boots, or can buy new ones, get the packable versions. They pack pretty flat. Get the gortex type waders vs the neoprene, again, they pack better. Instead of a vest I use a small chest pack. Holds two fly boxes and leaders/tippets. You can also just loop a lanyard around your neck and clip the fly box and leaders/tippets to it.
If you already have the retractable rods then ok, but, there are some really good 5 piece rods out there that aren't much. I have a 7wt that is good enough to land 3lb trout from the San Juan.