I hate to reply to myself. On Mon, 22 Dec 2008, lyricalnanoha wrote:
.org $0800
jmp relocate
.incbin "mybas.fp", $0002
xtrabyte: .incbin "mybas.fp", $0000, $0002
relocate: lda xtrabyte
sta $0801
lda xtrabyte+1
sta $0802
lda #<xtrabyte
sta $AF
lda #>xtrabyte
sta $B0
lda #$00
sta $0800
jmp $D912
it's "jmp $D566". -uso.