yes you can. I asked in the stockport decathlon store as I was looking at all kinds of combinations to accomodate my family of 5 and was told that any of the sides on the base standard and the full and xl and also the new 4:2 base vis a vis where there is one of those small little canopies over the door can be attached to another side of a tent that has the same corrispondiong small canopy. Does that make sense? They show this as "twinning" on the quechua web site where one canopy sits over the top of the other one so a neat seal is made,and the man in the store told me that all the tents have the same sized sides so that you can do any combination you want.
Hope that helps. Although I didn't see any of the combinations you propose the man in stockport did assure me it would work. I was considering attaching the standard bases as standing room bedrooms to the base xl but relised it was an indulgence too far as I have only recently bought a new family tent.
Claud
Thanks for the info we are hoping to get a 4.2 tent for the boys and the dogs, a XL base to live in and a standard base for us to sleep in but we are going to get it in stages so It won't feel so bad then!! My sister has these tents and loves them. We have only ever had a canvas tent, caravan or trailer tent so it will all be a very new experience. Thanks for the help.
Jo