two heads with one cab? Marshall or mesa?

[backyardburial]

Hi asked a similar question to this when I had two rectos, now its slightly different. I know my marshall 1960 cab is 300 watts and I think my recto cab is 240 (V30 speakers being 60 watts?)
This means per side in stereo the mesa cab is 120 right? Does this mean I cant play my triple recto (150 watt) through one side and my 100 watt marshall head thru the other? I assume the marshall cab is sweet, beinf 150 per side, but the wattage on the recto is too high for the mesa cab. Or is it only too high if the recto head is maxed? (which it never is). On the same note, in theory at least I can do this with my Marshall cab because its 150W per side?
I understand how this works in theory, but am I correct in thinking a 150 watt head is only 150 at its full capacity, meaning it WILL be ok with my mesa cab? Thanks, hope this makes sense!

 

[Jerrick]

Youll reach the max watts of your amp when its turned up all the way. And I remember reading that with Mesa at that point you are probably pushing more than what its rated at.

So as long as youre not cranking it too much, you should be fine.