Is it possible to configure bitcoind to allocate blocks in larger "chunks"?
If you referring to the blkxxx.dat file it will always have a maximum size of 128 MB which is defined in the bitcoin the source file validations.h

static const unsigned int MAX_BLOCKFILE_SIZE = 0x8000000; // 128 MiB


Also in this file you can see that the maximum pre-allocation chunk size fixed.

static const unsigned int BLOCKFILE_CHUNK_SIZE = 0x1000000; // 16 MiB