While the factory preset relic mode accepts some negative VDI numbers, it doesn't accept all of them. Also, mixed-mode is off by default.
I don't know your relic hunting experience level, so won't try to tell you how to hunt. However, if you want to find everything, you have to accept everything. And if you want to get deep, you'll need to use the all metal mode.
To achieve this I recommend the following settings:
BASIC ADJUSTMENTS:
TARGET VOLUME 48 - 63 56
AUDIO THRESHOLD 0 - 42 12
TONE (AUDIO FREQ.) 0 - 255 231
AUDIO DISC. ON/OFF ON
SILENT SEARCH ON/OFF OFF
MIXED-MODE ON/OFF ON
A.C. SENSITIVITY 1 - 85 68
D.C. SENSITIVITY 1 - 60 40
BACKLIGHT 0 - 6 0
VIEWING ANGLE 1 - 25 25
PRO OPTIONS:
AUDIO RATCHET PINPOINT ON/OFF OFF
S.A.T.SPEED 0 - 10 5
TONE I.D. ON/OFF OFF
V.C.O. ON/OFF ON
MODULATION ON/OFF OFF
G.E.B./TRAC AUTOTRAC ON/OFF ON
TRAC VIEW ON/OFF ON
AUTOTRAC SPEED 1 - 20 8
AUTOTRAC OFFSET -10 - +10 0
TRAC INHIBIT ON/OFF ON
COARSE G.E.B. 0 - 255 AUTO
FINE G.E.B. 0 - 255 AUTO
DISCRIM-INATION DISC. EDIT REJ. -95 - -39 ACC. -40 - +95
BLOCK EDIT
LEARN ACCEPT ON/OFF OFF
LEARN REJECT ON/OFF OFF
RECOVERY SPEED 1 - 40 30
BOTTLECAP REJECT 1 - 20 1
HOT ROCK REJECT 0 - 20 10
SWEEP SPEED 1 - 20 1
GROUND FILTERING 2 - 6 3
DISPLAY VISUAL DISC. ON/OFF ON
ICONS ON/OFF OFF
V.D.I. SENSITIVITY 0 - 99 80
D.C. PHASE ON/OFF ON
GRAPH AVERAGING ON/OFF ON
GRAPH ACCUMULATE ON/OFF ON
FADE RATE 1 - 14 7
PREAMP GAIN PREAMP GAIN 1 - 4 4
MULTI FREQUENCY METHOD 2 FREQUENCY (BEST DATA) ON/OFF ON
2 FREQUENCY (CORRELATE) ON/OFF OFF
V.D.I. NORMALIZED ON/OFF ON
1 FREQUENCY (3kHz) ON/OFF OFF
1 FREQUENCY (15kHz) ON/OFF OFF