You will likely find that if your duplicate track follows too closely behind the original, phase-cancellation will occur, making the audio actually sound unpleasant, and as the space is increased, a slap-back effect begins to occur. I've never liked this method anyway. For a fuller, warmer vocal sound I've found the Classic Chorus can work very well.
Start off by setting the delay to around 35 ms, rate at 0.2Hz, depth 15%, and mix at 1:1. You can then tweak to your personal taste. I've found these settings are like a mega-tight double-track. Activate the 'Spread' button for an even fuller stereo effect. You will find that as you reduce the delay time the phase cancellation starts to come into play, causing the warmth to be lost.
The Acoustica Chorus is no good for this purpose because its rate is fixed too fast, with no means of reducing it.