need help for the hashcat setting

[gotohack]

I want to do bf 26401 this hash mode data,and if I know the plain key first 8 bytes and last 8 bytes are same,how can I set the hexchar mask for this type?
I tried -1 charsets/DES_full.hcchr --hex-charset "?1?1?1?1?1?1?1?1?2?2?2?2?2?2?2?2" but have error "Custom-charset 2 is undefined." 
does anyone know how to make this setting..thank you

[gotohack]

I tried this command
./hashcat -m 26401 encrypted_2.txt -o cracked5.txt -a 3 --hex-charset ?b?b?b?b?b?b?b?b?b?b?b?b?b?b?b?b -w 4 -s 1000 -n 32 --force --session=v20
but it have a error Integer overflow detected in keyspace of mask: ?b?b?b?b?b?b?b?b?b?b?b?b?b?b?b?b
tried other command
./hashcat -m 26401 encrypted_2.txt -o cracked5.txt -a 3 -1 charsets/DES_full.hcchr -2 "?1?1?1?1?1?1?1?1"--hex-charset "?1?1?1?1?1?1?1?1?2?2?2?2?2?2?2?2" -w 4 -s 1000 -n 32 --force --session=v20
still have Integer overflow detected in keyspace of mask: ?1?1?1?1?1?1?1?1?2?2?2?2?2?2?2?2