You might be better off simply using the hardwired LFO2>Cutoff1/2 parameters, although using LFOAssign>FiltEnvAmt might at least be an interesting experiment
Don't forget that you can select a different polarity to each filter in the FilterEdit menu, which can produce some interesting results.
There's also nothing to stop you assigning the Amp Envelope to modulate Cutoff1/2 via the mod matrix either...