Jim, looking closer at this... is the rubber tubing really necessary? I understand what you're saying, but while you're on the move what's the chance of cold air coming in compared to the exhaust gases going out? I would think the chances of that would be pretty slim wouldn't it? Or was this a situational thing at the time you did it?
Basically I can't use the Innovate clamp on my pipe as it has a reverse megaphone on the end, so I'd need to make something up. I'm thinking a simple length of galvanised steel pipe (easy to get hold of) with a bung welded in stuffed as far down the pipe as I can get it would do the trick, along the lines of what you've done there.
You can't just but the bung right at the end of the pipe, it needs to have at least some distance to keep the fresh air away; If you put the bug up near the collector then you have 2-3 feet of extra distance. So adding 2-3 foot of hose is trying to replicate that. Exactly how far is required that is difficult to determine (without a dyno). Adding a little extra hose caused little problem. I would rather do that than risk having fresh air come back into the O2 sensor and corrupt the measurements.
You are always in danger of a Leo's attention when doing these types of measurements ; best to keep them to a minimum.