[NTG-context] Vertical alignment in combinations?

Today I feel like a total ConTeXt dummy... The problem: I have 3*1 combination where the end graphics are the same size, but the middle graphic is much shorter. With a standard \startcombination\stopcombination I can easily get all three side-by-side, but they are bottom-aligned while I'd need them middle-aligned. I thought I once had a solution to this, but can't find it - and, for once, the garden doesn't seem to be able to help. Is there a setting I can use to fix the vertical alignment? Or should I give up with combinations and go for a natural table instead? Or do something totally else? Thanks, Mari