The manual recommends the RMP or EXP waves, which makes most sense to me. Anyway I have finally sussed it, I just needed to crank the LFO mult up to 64x.

I can recommend trying this as the different envelopes make a noticeable difference to the sound (you can achieve that piano plink sound) and there is also a noticeable difference between using the RMP or EXP waves.

The following settings work well

Amplification page

ATK- 0, HOLD-127, DEC-64, REL-53 (or to taste)

DIST- -11, VOL- 70

LFO page

PAGE-AMP, DEST-VOL, TRIG-ONE, WAVE- EXP or RMP (EXP is sharper sounding)

MULT-64X, SPD-80, INTL-0, DPTH-127 (or to taste)