1951 G3LS front wheel brake drum offset

[murraymck]

Does anyone know what the correct offset is for the front wheel brake drum? I am rebuilding the front wheel as the existing rim is badly rusted and I suspect buckled. I'm replacing the rim and spokes with stainless ones. Measuring with a straight edge across the drum to the rim there is a difference of around 13mm between each side. I wasn't comfortable with trying to average out the error. I wasn't able to spin the wheel as the bearings were very tight and I had to strip the hub.

Thanks
Murray