(c) Ian Vincent 2005
Here are tips and information provided by others in the industry. If you have something to share, contact me and I will put it up.
From Dan Vigo (KTS) -  Length of Cap wire  :

I was doing this late June July an uphole test in Sudan, consisting of 15 upholes 80 meters deep. What happens is that some time we were having the first 4 shots not firing.
The cause of the problem was in the CAPS.
We had 2 different sets of caps, French and Chinese.
The French caps will stop blasting when the wire length is above 65 meters and there are four caps connected together. That was the reason of the miss fire.
We were connecting 4 caps and just wrap around the other 8 caps. The French caps will never blast when the wire lengths get above 65 meter. The solution is to connect maximum 2 caps. The French doesn't blast even if u connects a car battery!!!
The Chinese CAPS, will blast without any problem. And actually we find out while we were doing this investigation that they really blast easy.
So keep your handling procedure very tight when dealing with the Chinese CAPS.

Seismatters: Interesting story. The usually accepted  'proper' method of firing multiple caps is to connect them in series. With long leads, specific caps and probably specific types of blasters (voltage is important here) a series connection may result in a missfire. Maybe, connecting the caps in series downhole, at the charge might work, but it is not recommended practice. It would be interesting to know the manufacturer and type of caps involved, but I guess 'French' will have to suffice. (I'll leave it to others to make the jokes about whether things French work or not).
Likewise the type of blaster involved. I suspect that a High voltage blaster like the ShotPro would fire the caps. Some blasters used for uphole/refraction work are not really 'High Voltage' types.