If you are willing to House Rule, you could base the difficulty on a combined Silhoutte and Speed. Start at a base difficulty (2?) then have Speed increase difficulty by a certain amount while Silhoutte decreases it by a certain amount.
If you are willing to House Rule, you could base the difficulty on a combined Silhoutte and Speed. Start at a base difficulty (2?) then have Speed increase difficulty by a certain amount while Silhoutte decreases it by a certain amount.