And the 'lagg' problem has been solved.
The solution was to put the LINECOUNT and the SETTRIG lines in between the RUN_FIND and GET_OFFSET:
VISION RUN_FIND 'LETTERS'
LINECOUNT[1]=R[1]
SETTRIG LNSCH[1] R[1]
VISION GET_OFFSET 'LETTERS' VR[2] JMP LBL[99]
PR[5] = VR[2].OFFSET
SELBOUND LNSCH[1] BOUND[1]
I can now run it on a speed of 9.