Don't know about a 8'' or 9'' drop, To easy to do it with the frame... As far as making axles,,, Someone makes dropped axles,, Why can't you.. They are just another man making axles.. Make a jig and build them.... Don't let all the BS stop you if that's what you want to do... ''set no limit's on yourself''
I look at things like this....I have this rule I live by.. If another man can do it... I can too..
I really don't see where anyone needs a 8'' over a 6'' dropped axle... I build custom frames and can set the frame on the ground with a 6'' drop...