Ended up doing a different type of O-ring hangar on this, mainly because there just isn't alot of structural "meat" at the fuselage bottom to make hard points for the O-rings the way I usually do. Normally, It would be using a pair of screws and washers on either side of each "hanging station", then the O-ring just goes around the pipe, with a twist or two on either side, then under the washers and snugged up. Here, I ended up making centered hard points. The aft one is designed to both suspend the pipe and to maintain some "tug" forward to keep it from sliding aft. That one is just a little eye hook to grab the ring. The other one is a screw/washer (silver soldered together) and the O-ring is double looped under it to stay put and then the pipe is slid through. Looks like it will work, but I will be grinding the head of the screws down to give more clearance and avoid wearing a hole through the pipe. This isn't exactly what I thought I would do when I started the project, but should work. I would like to see other solutions to this.