The Regatta is a single room tent, but the other one listed will be a multi room tent. The carpet in this case will just be for the living area.
TBH I wouldn't even bother with a carpet, they're totally unnecessary. I've never used one in my life, & would only really consider it in the depths of winter.
Also, the regatta doesn't have standing height, so I doubt you'll be spending much time in there really. Carpets are really intended for tents you can walk around in, & are a pretty modern thing (none of this in my day

).
If you really do require some comfort, I would recommend you just get yourself a couple of the cheaper plastic backed picnic rugs & space them as you see fit. Or some cheapo floor rugs from somewhere like Ikea, plenty of people use these.
Most tents don't have carpet in the whole tent anyway, as it's a bit of a waste under beds etc.
At least picnic rugs can be used for other purposes & in other tents. Far better solution IMO.
4 Canvas tents (various sizes)
3 Plastic tents (various sizes)
& 1 Tin tent (yes, I'm a turn-coat, but it has a canvas awning)
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