location of LWCO

STEAM DOCTOR

i need to replace an old LWCO. the boiler was bone dry and the burner kept firing. the old lwco is a float type (McDonnell 67). the boiler has a marking for normal water level and a marking for lowest safe level. there is a little more then 2" between the 2 markings. there is a tapping  at the level of the lower marking. would this tapping be the appropriate place to put a probe type lwco. my supplier says that the probe type needs to be lower then that marking. if i cant use this tapping would it be okay to just replace the 67 with another 67. thanks.

PS i found a number of leaks in the system which i have since correted