I will have to cut though a double wall on a very nice stack to direct it up the funnel. If I was gpoing to stay on non condensing it wouldnt be as big a deal but I want to set it up to run on saltwater eventually and then I will have a gaping hole to deal with..........
I have been thinking about this very issue as I guess that I will do the same and start puffing with condensing later.
Do have a look at your boiler casing. It may be possible to make a hole in the casing and run the exhaust across to a position below the funnel stub. I think that should be possible in my case, but will need to do some drawing to be sure.