Hoghead,
The snail balancer is actually brilliant in my opinion and money well spent. In particular if you have not had years of experience balancing multiple SU carbs. I have a BJ7 and the tool is incredibly accurate albeit as you say, awkward to use unless.... I used a mirror on an expandable rod (most of us have one) for a while and was able to read the gauge. Then I went to an auto parts store and got a top radiator hose with a 90 degree elbow which fitted snug into the snail, with this I can easily read the gauge between the two SU's.
I have been tuning my car for over 20 years and tools have ranged from a piece of garden hose and coat hanger wires in the dash pots tops, to a Gunston colour tune and a unisyn with the tube and orange bead. While my carbs are fairly well synchronised and tuned (I thought for fifteen years), a friend gave me a snail flowmeter when he sold his car and I gave it a try just for fun. Amazingly, I found the STE snail to be the best of all the tools and I would now give everything else up if I had to choose just one tool. If I tune with all the other gadgets and get them as best I can (including by ear), I then put the snail in the inlet and even the very minor gauge differences can be seen. I can tune to get the exact same readings easily and my carbs have never been happier. Even one eighth of a turn on the screw will change the reading by a very visible amount.
The only tools I use now (for around 5 years) and I believe the most effective for me are the STE snail and the rod/wires which go in the dashpot (they come in the blue plastic sleeve tool kit).
I'm sure many will not agree and at the end of the day it is all individual choice, I just wanted to give a plug for the poor old snail.
Cheers
Tony