After a simple google search. I don't know if this affects the strength of the transmission or not.
A spool or full lock puts lots of strain on the axle... that diff in a legacy is only designed for 50% power. These guys might have a spool for ya...
If the power train holds up to it, imo go for it.
I am interested in this for a solid axle 4wd conversion idea... Otherwise I wouldn't care that much.