lowdown on double blades ???

[n2audio]

i have read here that some of you guys use a double blade set-up under your decks. can this be done on any mower? i seem to recall hearing that some of you use a high lift on top and a gator on bottom, setting the blades in a cross + pattern. would any changes have to be made to the deck? what about spindle life when turning two blades?

thanks in advance for all the advice.

(im running a 48" jd if it matters)