OP already answered in post 44 that it actually worked, although with PA and controlled volume.....
...nevertheless, as also an OWNER of two slanted and one straight Marshall cabs, I can say this:
1) One half stack looks like a slightly over-sized combo amp, that is almost wimpy, so two half stacks is double wimpy; but one FULL stack is what REAL MEN play! (before upgrading to a wall which consists of full stacks, not half, never have a row of half stacks created a wall, a hedge at best)
2) The sound will become more pleasant (less fizz) in a full stack mode. Why? A guitar player can (finally) hear all the treble they've been killing the front row with before, and will adjust accordingly
3) +1 on phase issues; also a full stack works like PA's line array: setting up speakers vertically expands horizontal coverage, two half stacks spaced apart are like two narrow cones in two different places, makes absolutely no sense.
BONUS TIP: emptying the bottom cab and turning the top 4x12 into a diagonal 2x12 will a) put money in guitarist's pocket for the sold speakers, b) make the top cab lighter without taking away functionality, c) make the bottom cab from just a cab into a cable box, stage prop and amp stand at once!
...nevertheless, as also an OWNER of two slanted and one straight Marshall cabs, I can say this:
1) One half stack looks like a slightly over-sized combo amp, that is almost wimpy, so two half stacks is double wimpy; but one FULL stack is what REAL MEN play! (before upgrading to a wall which consists of full stacks, not half, never have a row of half stacks created a wall, a hedge at best)
2) The sound will become more pleasant (less fizz) in a full stack mode. Why? A guitar player can (finally) hear all the treble they've been killing the front row with before, and will adjust accordingly
3) +1 on phase issues; also a full stack works like PA's line array: setting up speakers vertically expands horizontal coverage, two half stacks spaced apart are like two narrow cones in two different places, makes absolutely no sense.
BONUS TIP: emptying the bottom cab and turning the top 4x12 into a diagonal 2x12 will a) put money in guitarist's pocket for the sold speakers, b) make the top cab lighter without taking away functionality, c) make the bottom cab from just a cab into a cable box, stage prop and amp stand at once!

