Instabuddy gets physical contact until I’m confident he/she is calm and wont bolt, then we can spread out or swim side by side if needed. That said, I usually dive with people who can do a controlled ascent face to face in horizontal trim a few feet apart. We tend to practice gas shares frequently as well, quickly at the start of the dive and sometimes longer on safety stops. The last time I dove a single tank with a pony and an instabuddy who needed gas donation (4-5 years ago) I handed her my 40” pony hose and she swam to shore with me on my left side (where the pony was slung). She was calm but low on air, we still had a bit of a swim to shore with a virtual overhead (river drift dive with heavy boat traffic precluding a direct ascent) and I wasn’t sure sharing my single tank would leave enough margin for error at that point, so this seemed like the best option (pony bottle was an AL40). Being a virtual overhead dive, redundant gas (pony or other) was strongly suggested by the club organizing the dive but my buddy who I was assigned last minute didn’t heed the warning. She actually asked me “what’s with the extra tank?” with a smirk right before the dive! The irony.