I get the floating issue, it sucks. I currently wear a packer with an O-ring that has some fabric tabs I cut out from a pair of Tranzwear boxer briefs. I just safety pin it on and it mostly stays put in my boxer briefs. I use it with my Reelmagik Basic Packer, the new softer version. Placement is key though. If I pin just a tad too high, then everything gets weird. So YMMV.
🔗 [Link: imageshack.com/-%3E-bleeped-%3C-.us/v2/150x100q90/922/q9F4Fn.jpg%5B/img/] 🔗 [Link: imageshack.com/-%3E-bleeped-%3C-.us/v2/150x100q90/924/bJMlkg.jpg%5B/img/]Prior to this I made an easy DIY harness from elastic bands. That worked amazingly well at keeping things in place. You could use that thing and confidently wear boxers. It helped when my dysphoria was a little worse too since I sit to pee. I wouldn't be detached upon pulling my shorts down. It's a PDF download link here under The World's Simplest Packing Harness. The only downside was damage to the shaft base of the packer. At the time I was using an extra small Mr. Limpy.
http://www.->-bleeped-<-.html#harnesses
Hopefully this was helpful.