He wanted to take no risk,however small.
既然你都知道是省略了it is了,为什么一定要考虑是不是让步状语从句呢.
要是非推敲的话,应该是,因为however small算是省略句,省略句也是句子,既然是句子作的状语,那就是状语从句
I'll start in a few minutes,___dark it may be.
确实应该是however
as在句首的时候,肯定不是引导的让步状语从句,理由是
as引导的让步状语从句,要求必须倒装
though随意,although绝对不可以倒.
1.表语+ as+ 主语+谓语（当表语时单数名词时,省略不定冠词）
Child / young as he is ,he has known a lot.
2.副词（通常是much）+ as+ 主语+谓语
Well as he does in study,he is not arrogant.虽然他功课很好,却一点都不傲慢.
Much as she loved him (=Though she loved him very much),he deserted her in the long run.
3.动词（try）+ as+ 主语+谓语
Try as I might,I cannot lift it
虽然我试,但还是搬不动.