If this is the single seat, then you ought to be able to do some searching in the used/discontinued bins at shops and find something to mount to the fender struts pretty easy (HD's over the years had thse smounted here -- especially older FLH's). That would be preferable to using the back rest, and stronger.
If you look here, http://mojoincolorado.spaces.live.com/, you will get an idea of what I did. A bit heavy as I used solid versus tubular steel, and the fender itself doesn't have the lateral strength I would like, but has worked excellent so far. (I hate to say it, but you must use the IE browser to see it as microsoft is the page provider.)
[ This message was edited by: Mojoinco on 2006-11-14 13:15 ]
If you look here, http://mojoincolorado.spaces.live.com/, you will get an idea of what I did. A bit heavy as I used solid versus tubular steel, and the fender itself doesn't have the lateral strength I would like, but has worked excellent so far. (I hate to say it, but you must use the IE browser to see it as microsoft is the page provider.)
[ This message was edited by: Mojoinco on 2006-11-14 13:15 ]