'The alternative is to get someone to use heat to put a side bubble in the perspex lid but I don't know anyone who could do that! (Though may be the simpler option).'
I ran into a similar problem when I recently mounted a second arm on my 80's plinthed Gryodec for a mono setup. The issue was not with the counterweight but at the opposite end of the arm at the rear of the table where both the upright section of the plinth and the dustcover were in really horrible positions.
Although sacrificing a bit of efficacy in terms of dust sheltering, the solution was to take the table to a local plastics fabricator and have them cut out a small section of both the plinth and the dustcover. They did an excellent job (they had custom built the dust cover for me a number of years ago when I replaced the original) and I'm happy with the result.
If you really like the arm, worth considering and probably more attractive in the long term than a "bubbled" dustcover.
http://www.canuckaudiomart.com/view_userimages.php?user_id=2507&image_id=19556
I ran into a similar problem when I recently mounted a second arm on my 80's plinthed Gryodec for a mono setup. The issue was not with the counterweight but at the opposite end of the arm at the rear of the table where both the upright section of the plinth and the dustcover were in really horrible positions.
Although sacrificing a bit of efficacy in terms of dust sheltering, the solution was to take the table to a local plastics fabricator and have them cut out a small section of both the plinth and the dustcover. They did an excellent job (they had custom built the dust cover for me a number of years ago when I replaced the original) and I'm happy with the result.
If you really like the arm, worth considering and probably more attractive in the long term than a "bubbled" dustcover.
http://www.canuckaudiomart.com/view_userimages.php?user_id=2507&image_id=19556