Dear Wing,
Not at all. The added load is the plank. I usually shoot in the afternoon for 2-3 hours and there are no problems carrying the set-up around. Worth mentioning is the 501 video head. The locks fasten well, so tilting, dropping and pivoting around the central axis happen scarecely.
I made the plank in order to accommodate with the use of a DSLR on the fieldscope. The fieldscope sticks fast to the wooden plank but because my fieldscope is an angled one, it is difficult to prevent vibration when a DSLR, an AFD 24-50mm Nikkor zoom and a DIY adaptal ring are further attached to the fieldscope; these additions will be hanging in the middle without a good anchorage point to the plank or the tripod for the purpose of stabilisation. At the same time, with these items added, the whole set-up will become pretty bulky and heavy. And worse still is that the advantages from such a set-up do not outweigh the ones from using the prosumer dc.
I am no good with carpentry. Perhaps, if the plank can be made into a double-deck one, with the lower one for the fieldscope and the upper one for the DSLR attachments, vibration can be reduced. Or, simply, if I just use a straight fieldscope, the problem can be resolved.
Pete