Looking good - I've ran bench with the changed defines and no other changes on the cards I had. Two of them were with odd partitions initially.(they were bootdisks for a raspberry pi) I ran each test twice.
[MicroSDHC 4G class 2 in adapter, 56MB partition]
Type any character to start
Free RAM: 62747
Type is FAT16
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 866.16 KB/sec
Maximum latency: 183747 usec, Minimum Latency: 31926 usec, Avg Latency: 37813 usec
Starting read test. Please wait up to a minute
Read 2547.93 KB/sec
Maximum latency: 13355 usec, Minimum Latency: 12608 usec, Avg Latency: 12860 usec
Done
Type any character to start
Free RAM: 62747
Type is FAT16
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 861.76 KB/sec
Maximum latency: 173563 usec, Minimum Latency: 32131 usec, Avg Latency: 38007 usec
Starting read test. Please wait up to a minute
Read 2550.53 KB/sec
Maximum latency: 13337 usec, Minimum Latency: 12609 usec, Avg Latency: 12846 usec
Done
[MicroSDHC 16GB Ultra Class 1 in adapter, 56MB partition]
Type any character to start
Free RAM: 62747
Type is FAT16
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 2971.38 KB/sec
Maximum latency: 77963 usec, Minimum Latency: 9330 usec, Avg Latency: 11020 usec
Starting read test. Please wait up to a minute
Read 3931.64 KB/sec
Maximum latency: 9612 usec, Minimum Latency: 8294 usec, Avg Latency: 8331 usec
Done
Type any character to start
Free RAM: 62747
Type is FAT16
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 2832.83 KB/sec
Maximum latency: 212444 usec, Minimum Latency: 9343 usec, Avg Latency: 11560 usec
Starting read test. Please wait up to a minute
Read 3931.64 KB/sec
Maximum latency: 9606 usec, Minimum Latency: 8293 usec, Avg Latency: 8333 usec
Done
[Standard SD card, 1GB class 2, partitioned normally, but only 30Mb free space]
Type any character to start
Free RAM: 62747
Type is FAT16
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 3157.74 KB/sec
Maximum latency: 202461 usec, Minimum Latency: 8545 usec, Avg Latency: 10354 usec
Starting read test. Please wait up to a minute
Read 4111.16 KB/sec
Maximum latency: 9299 usec, Minimum Latency: 7892 usec, Avg Latency: 7969 usec
Done
Type any character to start
Free RAM: 62747
Type is FAT16
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 3041.00 KB/sec
Maximum latency: 238158 usec, Minimum Latency: 8458 usec, Avg Latency: 10751 usec
Starting read test. Please wait up to a minute
Read 4112.86 KB/sec
Maximum latency: 8409 usec, Minimum Latency: 7897 usec, Avg Latency: 7964 usec
Done
[same MicroSDHC 4G class 2 in adapter as first test, but freshly formatted as one big FAT32 partition]
Type any character to start
Free RAM: 62747
Type is FAT32
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 1408.04 KB/sec
Maximum latency: 154868 usec, Minimum Latency: 19368 usec, Avg Latency: 23058 usec
Starting read test. Please wait up to a minute
Read 3303.33 KB/sec
Maximum latency: 10479 usec, Minimum Latency: 9780 usec, Avg Latency: 9917 usec
Done
Type any character to start
Free RAM: 62747
Type is FAT32
File size 20MB
Buffer size 32768 bytes
Starting write test. Please wait up to a minute
Write 1419.64 KB/sec
Maximum latency: 153552 usec, Minimum Latency: 19564 usec, Avg Latency: 22867 usec
Starting read test. Please wait up to a minute
Read 3304.97 KB/sec
Maximum latency: 10541 usec, Minimum Latency: 9837 usec, Avg Latency: 9912 usec
Done
Incidentally I am using 6 inch flying leads from the SPI port into a breadboard and an SD breakout. No errors 