Second dog, silly question...

[SinclairSpectrum]

Considering adding to the family with a second dog.
We have the space and time etc and I think Dog1 would appreciate some same species company.
I fancy a smallish dog - Cairn terrier sort of size but happy to adopt a rescue / shaggy Heinz type.
My silly question is this - Dog1 is huge, do I need to take the size difference into comparison? Would having 2 different sized dogs present practical problems with walking / play?
Would really rather not get another big dog - there'd be no room left on the sofas for people.

I don't think it's so much the size difference you need to take account of, rather different energy levels and play styles

For example my dog is medium height but quite slight so frequently gets bowled over by big labs so I wouldn't get a big, chunky dog that liked to body slam as my dog would spend every walk flat on his back!

Some bigger, calmer dogs do fold up remarkably small whereas some smaller breeds seem to take up an amount of space completely out of proportion to their size ...

We recently got a third dog. She is tiny. The other two are big labs. She plays lots with dog 2 (dog 1 is older and doesn't like dogs), her size doesn't seem to matter. What I do notice is she plays different games, she likes to run rings round him and she jumps up and hangs off him (trying to stop her doing that). She doesn't have the retrieving gene, she's got flattened by both labs once or twice as she's stood and watched when a ball was thrown!

Age is a bigger factor, as I mentioned, the older dog is growing out of the playing stage. I like having three different ages, mine are two, six and ten yrs.

Noitsnot is right their size doesn't make much difference. my little ddog is a jackhuahua (chihuahua cross jrt) and plays with my father's whippets and his Japanese Akita just fine.
He happily plays chase with the whippets although he never catches them and play fights with them and the Akita he's never got hurt.( he's quite the little terrierist)
If your going for a small dog to match with a big dog I'd personally go for a terrier or terrier cross, most terriers I've met are quite hardy and fiesty and have big dog personalities.