I saw where one person had stacked two subs and strapped them down to a four wheeled dolly. Looked like they deployed and used them right on the dolly. Any down side to this idea?
Mark,
Big downside is stability of the stack, especially if you are using pole-mounted tops above.
Castors can/will rotate inward, reducing the footprint by a large margin.
For truck packing and transport, it is generally preferable to have the casters swivel out no further than the dimensions of the cabinet to avoid hang-ups.
The QSC KW181 is only 23.4" wide, if typical 4" casters were deployed as above, the caster's point of contact with the deck if you were to toe them both out (extra work) would be about 19.5", while "pigeon-toed" in (like they always seem to end up) the distance between point of contact is only 14".
A 14" wide base would make a stacked pair with a pole mounted top like a domino ready to topple.