All of this can be done equally, or even better, from a standard overhead join. I don't understand all this fuss, neither do I see any advantage to a deadside join vs. an overhead - overhead join is published standard, 500 feet above circuit, though it can of course be overridden by local practice but then this should be published. And how are you going to check the signal square from a deadside join?
The only reasons for NOT joining overhead are glider winching and parajumping - both should be covered by adequate published procedures. Or am I being naive?
Jan, That depends; have you much personal experience of deadside joins?
I was taught and have taught both, being military and civilian instructor qualified. The military would teach an overhead join to a low-time student but expect more advanced students to carry out a deadside join, obviously only if there is a radio frequency and the duty runaway is known.
Overhead joins can be dangerous where two aircraft are joining at a similar time. Pilots' attention is diverted from a lookout for other aircraft as they organise themselves in the overhead for the correct runway. As you say, they look at the signals square, where fitted, and the airfield layout, at the very time they might be converging with another airframe doing the same thing, from the same place. During a deadside join there is a blind spot under the aircraft. Because the join pattern tends to be fixed and rigid in some pilot's minds, they do sometimes tend to cut in ahead of other circuit traffic.