HCA: Hermit Crab Association

I have had my crab Beauty for a couple of months now, and I was thinking about seeking a companion for her. However, last week she buried herself and I haven't heard her moving around, nor is there any sign she has come up during the night, so I think she's down for a molt. This didn't completely surprise me, as she'd been digging test holes for a couple weeks and got very lethargic for a few days before she disappeared. It's her first molt with me (yay!) but she had a successful molt right before I got her from her previous owner, so I'm not too worried.

My question is, if I were to find a companion for Beauty before she comes up from her molt, is it safe to introduce the new crab to the tank while she's buried? I have a 20 gallon tank with about 6 inches of substrate, and she's a large-ish crab (I measured about a 2 inch leg span when I got her, but she wasn't a fan of the measuring tape and is probably a bit more when relaxed). Tank conditions are stable at 75-80 degrees and about 77% humidity. I would be looking for a crab no larger than Beauty.

You could definately add a crab while one is down. Give the new one a quick dip in the fresh water so they smell like the tank.