Tour paks have different mounting holes drilled into it to move either the single or the double mounting about 1 inch either forward or backwards...don’t ask how I know....

Just did this to my bike... it all depends on the person’s physical build lol I used a HD solo rack, the stock factory king tourpack with speaker pods, stock handle bars, HD signature series solo seat, on my 16 RGU. Slid all the way forward on the solo rack, the tour-pack was about 2 1/2” too far back for me to utilize it for a backrest while riding... but a buddy of mine, with monkey arms said it felt great to him. We’re both about 6’ tall. With that set up, I could fit the seat’s backrest on the bike with the tourpack (like r0de runr above) in place still and that felt fine... but I wanted the cleaner look without it... so I got some steel out. Without any serious mods to the solo rack itself (just drilling a couple holes), you can easily move the tourpack 2” to 2 1/2” forward. But anymore than that the solo rack starts coming out beyond the back edge of the tourpack. If the stock setup doesn’t work for you, it’s easily modified... all depends on the specific persons reach, handle bars, type of tourpack, seat, etc.