#1
Hello there, i'm going to tune my guitar a half step down from standard tuning.
But i have 0.09 gauge strings, will it sound good with so light strings or should i change to more heavy strings?
#2
It should be fine, maybe .10s would be better. I've played Eb with .09s and it's not THAT bad.

It's all preference, try it out yourself first
Gear:
.Fender Classic Series '70s Stratocaster
.Peavey Classic 30
.Xotic BB Preamp
.MXR Carbon Copy Analog Delay
.Vox V847A Wah
.Boss RC-2 Loop Station
.Washburn WI-24 (first guitar )
#3
i play a half step down with .09s they sound fine. its all a matter of opinion. but i like them that way.
#4
Half step down with 9's is fine, a lot of people use that setup. I switch mine between and standard and 1/2 step down and use 9's
2003 Music Man Axis Pacific Blue Burst
#5
shud be fine. anywhere after D standard is when i usually change guages
Equipment:

ESP F104 Bass
Spector Legend 5 Classic Bass
ESP B206SM Bass
Axl Mayhem Fireaxe Guitar
Gallien-Krueger 400RB-III Combo Bass Amp
Gallien-Krueger 115SBX Bass Cabinet