thanks DMac. i used Ness fillers which are one piece they do not go all the way up to the seat. i do not know for sure since i have never tried, but you may be able to still use a backrest and take it on and off without any issues or need to move the fillers. again i have never tried, since i got this done a few days ago. i do not usually ride with passenger, so wasn't much of a concern for me. the 2 piece filler set...uppers can be removed easily without tools. the lowers i believe require drilling and most likely requires tools to remove.