http://sirsql.net/blog/2011/9/26/optimizing-database-restores.html
BTW, I did find that increasing the thread count helped a lot too. It did increase the buffer count to by 6 * Threadcount up to 28 buffers max, which sped the redo phase up. But I do think that that if SQL Server allows up to a 4MB transfer size natively then Red Gate SQL Backup should allow it too. I'm not suggesting that you change the 1MB default, but should allow for manual adjustment of MaxTransferSize and buffercount parameters.
BTW, I did find that increasing the thread count helped a lot too. It did increase the buffer count to by 6 * Threadcount up to 28 buffers max, which sped the redo phase up. But I do think that that if SQL Server allows up to a 4MB transfer size natively then Red Gate SQL Backup should allow it too. I'm not suggesting that you change the 1MB default, but should allow for manual adjustment of MaxTransferSize and buffercount parameters.