__vector(ubyte[32]) misalignment

[Bruce Carneal via Digitalmars-d-learn]

The .alignof attribute of __vector(ubyte[32]) is 32 but 
initializing an array of such vectors via an assignment to 
.length has given me 16 byte alignment (and subsequent seg faults 
which I suspect are related).

Is sub .alignof alignment expected here?  IOW, do I have to 
manually manage memory if I want alignments above 16?