Can the Leuckardt-Wallach method be used to produce larger quantities? (and why?)

[Microogata]

I've read (in ''Secrets of Methamphetamine synthesis'') that the Leuckardt-Wallach reaction (P2P and N-Methylformamide) is used to produce on a low scale (up to 1/2 lbs). Later on in the book, the author says that by using a ''European variation of this method'', it's possible to produce more than that. But the reason for the scale limitation of the L-W reaction isn't specified...
Wouldn't it be possible to simply proportionally increase the quantities of reagents in order to produce larger quantities ?

Also, is there any way to calculate the theoretical amount of a final product that you can get using a specific reaction ?
I know it's a naive question sorry, but I've just started to learn organic chemistry

 

[WillD]

You can scale

 

[Microogata]

So, just by proportionally increasing the quantities of reagents?

 

[WillD]

Yes. Only excess in especially large quantities can be reduced