Question: is the following tapetype (obtained with
amtapetype -o -e 4g -f /dev/nst0 -t LTX200G on
an Exabyte 1x7 LTO autoloader) on the list?

define tapetype LTX200G {
  comment "just produced by tapetype prog (hardware compression off)"
  length 201216 mbytes
  filemark 0 kbytes
  speed 31371 kps
}


The amtapetype command returned the following initially, before
writing out the tapetype configuration entry:

unknown: Empty amanda header: buflen=32768 lsize=10
0000000  \0 001 002 003 004 005 006  \a  \b  \t
      0100 0302 0504 0706 0908
0000012
unknown: strange amanda header: ""
unknown: Expected: "<Non-empty line>"  Actual: "<null>"
Estimate phase 1...
Writing 1024 Mbyte   compresseable data:  34 sec
Estimate phase 2...
Writing 1024 Mbyte uncompresseable data:  33 sec
Estimated time to write 2 * 204800 Mbyte: 13200 sec = 3 h 40 min
wrote 6422528 32Kb blocks in 98 files in 6411 seconds (No space left on device)
wrote 6455296 32Kb blocks in 197 files in 6732 seconds (No space left on device)

As usual, I had to turn off hardware compression with

mt -f /dev/nst0 compression 0

I seem to recall that this was the correct syntax, as opposed to

mt -f /dev/nst0 compression off

as the man pages for mt tactfully avoid specifying what the arguments
should be -- perhaps their author took "man pages" for "gentleman pages"
and prefered to be discreet.