Weight and grip of sarissa and shield in macedonian phalanx

[MeinPanzer]

But the question remains, how much space was then occupied by single soldier. Personally, I don't think that much less than Polybios three feet of frontage woulb be practicable. Warry's 0,5 (or rather 0,45 m) seems simply to restricting for phalangites to use their weapons.
About the term "synapsismos" itself - my Greek is not very good, so could you explain if it means literally "locked" or "close (one to another)" shields.

The Greek just roughly means "shields together" (syn "together" + aspis "shield").

As for the shields: In "Cambridge History of Greek&Roman Warfare vol I" in article about hellenistic military forces (Sekunda and de Souza) there is mention of three shields with diamter of 66, 73.6 and 74 cm (p337). Connolly after Asklepiodots gives 65-67 cm ("GRAW" p. 77) . Are there any other excavated shields of this kind?

Yes, there are. I can't remember which examples Sekunda actually mentions, but whole or fragmentary shallow and rimless shields (presumably peltai) have been found at Pergamon, Dion, Vegora, and recently at Staro Bonce in FYROM, and then there is also the example with the embossed name of a king Pharnaces which is in the J. Paul Getty museum. The latter shield is around 80 cm in diameter, which would place it in the low range of hoplite shield sizes. Connolly's proportions are based on the example from Pergamon.