TO-3 power transistor orientation

In power amps, from memory, I've only ever seen TO-3 power transistors orientated with the 'top hat' section upwards when horizontally mounted on heat sinks.
I assume there wouldn't be a problem mounting them 'upside down' with the terminals at the top?
The reason for doing so is that I need more clearance between the connecting leads and the amp boards themselves.
So I thought it better that I should ask before trying.
 
Thanks for the respondents thus far.
Not knowing how these transistors are fabricated (or more so how the chips are bonded to the shell) and would affect the bonding.
I thought this would be the case.
If it wasn't I guess that they wouldn't work in the Southern Hemisphere.

Thought it circumspect to add a :D for the later comment
 
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A To3 has the emitter and base pins offset so that it cannot be inserted the wrong way around.
But if you offered up from the reverse side of the board you would be swapping the emitter and base leads.
You would need to redisgn the layout to specially suit upside down mounting.

Thanks Andrew, taken care of.
The leads are 'flying' from the PCB to the power transistors so that's not a problem.
 
A To3 has the emitter and base pins offset so that it cannot be inserted the wrong way around.

Actually they can be. I once saw a TO3 transistor inserted in the socket backwards. They had to bend the pins to fasten the transistor to the heat sink. I called all the technicians over and asked what bleeping idiot did this. Naturally no one would admit to doing it. There's an old joke that you can't make anything foolproof because the fools are too ingenious.