as said above but remember most modern cars may have pre-tinted glass and may put some light tints over the legal limits, no tint is aloud on the windscreen in the field of view or wipers zone,

i have 50% in the rear and rear sides while having 25% but the st has about 10% in the glass
its not so dark that i get pulled even though i could if the get funny and the 2 colors don't look odd, (i think to go black on the back and a light tint on the front looks odd)
could try black rear, dark rear-sides, and med/light fronts,
light colored cars, and dark interiors can make the kits look darker,

if you do get pulled by police and they don't like Ur tint they can ask you to have them checked/and removed, make you remove them on the road, if they are bad and classed as dangerous a fine and may impound the car, not sure if they can give points yet?