I do my cold smoking at ~68-78°.
I use a MES 30, which I've modified to be able to control the Sub-100° temperature.
Cold smoking, by the definitions I've seen, is < 100°.
In your case, a tube set in the bottom should work fine. I use an
AMNPS, and a Mailbox Mod for mine.
But your target is to stay below 100° for Cold smoking.
Cold Smoking penetrates all the way through the bacon. (Ref: daveomak)
Smoking with Pellets dissolved into sawdust and dried makes great cool smoke. Not sure if that works out in a tube.
For me, I think 6 hours of Apple Wood sawdust was just dandy for flavor. I did my two most recent slabs to two 6 hour smokes and the Jury is still out. It's finish aging in my curing fridge, and will be sliced for Christmas feast with the Family.
Along with some single smoked.
I like it, the wife and 3 littlest Grandkid's like it. So if nobody likes my double smoked, I guess I'll have a lot of bacon to enjoy. ;)
Warm smoking is another way. But I'm not versed in that.