I offer my choice in gear configuration as one I believe is "as good as it can be" for when your buddy is not available. All diving here is wetsuit, the water is still in the 80's at 100' ...I've never seen a single dry diver in the years I've been here. It's just not practical. I've also found that the GUE 30/30 rec triox mix is indeed much nicer to dive in the 80' to 120' range than even Ean 32 or 36. The flip side of that, is that it creates a virtual overhead. While GUE may use the term "specialised ascent techniques".... staged deco stops are the same thing no matter what you call them. (even if you do them on bottom mix as opposed to a gas switch & deco mix)
I like my kit to be as consistant as possible regardless of whether I'm diving a single or doubles .... same inflators , same reg positions, same gage positions, etc. To that end, I keep my transpac2 set up for singles and the transplate for doubles..rec wings for singles and supers for doubles..both have the same inflators and the same "feel" in your fingers when in use. The harnesses, crotchstraps, weight pockets, and D ring placements are identicle. I dive a long hose on the singles kit, same as the doubles, I have the backup on a neck bungee, it just comes off the pony on the singles kit. I prefer a console, so it's on the main tank, but I Also have an spg (comes over the left shoulder by the primary bladder inflator) for the pony. The primary bladder inflator is on the main tank, as is the norm, additionally, I have the redundant bladder on the pony, and it comes over the right shoulder, secured loosely by a bungee loop. Everything stays in place, no hoses hang out to become caught on something..The long hose routes the same as on doubles, the backup second stage hose routes next to my right side under my arm. The pony stays secured in a quick on/off bracket, so setting up is a piece of cake.
While I like having my favorite buddy dive with me best, I wouldn't have missed the last thousand or so dives I did without her.
Given reasonable circumstances and dive conditions, I fail to see where solo diving presents risks that can not be adequately managed with proper gear, training, and experience.
In most of those worst case scenarios that have been presented in opposition to solo diving, (heart attack, etc.) The only thing your buddy is really any good for is Immediate Body Recovery. I prefer to manage that risk with fitness, eating and living properly.
Here's a pic of the singles kit... I got my flame proof undies on...
Darlene