Tandem seatpost

I have a tandem, the front seatpost is 27.2mm but the rear is 27.0 with electrical tape wrapped around it.

The frame looks like it has been tightened with the 27.0 seatpost in and has been slightly squished.

I have got a 27.2 seatpost in a bit, and I can turn it when it has a saddle on, but I can't get it further in or out. Admittedly I have only had a quick go at it.

Any advice on how to proceed? My initial thoughts are to drink and beer and forget about it for a while

Thanks in advance

I got someone to sit on it and wrestled the new 27.2 one off.

Should I rewrap the old 27.0 one with tape and be done with it?

Maybe worth asking in the tandem thread in case frames with varying seat tube diameters actually exist, who knows?
Otherwise as you say the tube may have been pinched to suit a smaller post and no longer accepts its original size. If so that would be localised just over the height of the pinch bolt, you can try opening it with a flat screwdriver, but be very gentle. Or, if the seat cluster is threaded, screw the bolt from the other side while inserting a coin in the slot. This will give you to better control over how much you force the tube out, while maintaining it open as you insert the post. Do use grease anyhow and clean thoroughly the inside beforehand (with wire wool to remove any glue excess from the tape), also ensuring there isn't any small metal split bits from the previous misuse.
Finally, if you drink a beer, opt for s can, you can always cut shims from it if you need to maintain the smaller post, would work better than electrical tape!

Had missed your subsequent post...

The coin did the trick for getting the new one in. Not over confident of future adjustments! Thanks for your help

I had a similar problem a while back with an old Colnago frame I was doing up. I couldn’t get a 27.2 seatpost in so supposed it must be a 27.0 which fitted nicely but kept slipping. Eventually tried the screwdriver in the seat lug trick and the 27.2 now fits.