I'am thinking of putting a hand access hole in some 200mm NB heavy pipe for the one i'am doing next for the HEQ5, will just fill it with sand up to the hand hole point
. As for the top i'am just going to machine a peg up for it, piss easy. If its a long term temp or perm you could make another top plate and bolt top plate onto pier top leaving a small gap for adjustments, that's how alot of designs i've seen have being done.