Overfilling a Phantom bag (need advice)

refering to someone very knowledgable on this forum:

You will pick up ~2.6F for every ounce of [800 FP] fill that you add.

see http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=27480&skip_to_post=227472#227472

Another option would be to convert it to a quilt. You could save weight & add warmth due to optimal down placement.

So I think I'll put 3 ounces in then which, according to that math, will put it just under 24 degrees.

Now I just need to figure out how I want to gain access into the baffles without messing up the bag completely haha.

+1 on Bender's idea quilts are the way to go

The Reactor liner weighs 8 ounces. I'd ditch that, open your bag along the zipper, and add 4-5 ounces of down. Some people like quilts. I personally don't find them nearly as versatile as a bag. Undo stitching along zipper, stuff the down, and sew the zipper back in place. You'll cut 3-4 ounces from what you're already carrying, won't add more weight, but will have a much warmer bag.

Hi James, yes Brad is right in that the easiest way is to pull the zipper seam and fill the baffle openings created along this seam. Is the Phantom a full-length zip? Is there a cross-block baffle on the seam opposite the zip, or is there none, which would allow shifting down from top to bottom? If there is a full zip and no cross-block baffle it becomes much easier; the baffles can be filled from one side. If there is a cross-block baffle, the fill must be added to top and bottom. If the zip is not full-length, there will be a seam below the zip that must be opened to access the lower baffles. Overfilling the hood and footbox will be another magnitude of difficulty, and something I wouldn't try personally; you would move from one or two open seams to the bag nearly de-contructed if opening the hood and footbox dependant on their design and pattern.

Not sure of the zipper size, but if it's a five or bigger, you could replace it with a #3 while you've got the old zip removed. The weight loss of the lighter zip will offset the additional down to a certain extent.

Worked with down before? There are a few tricks to make the job easier; read Roger Caffin's MYOG article on down quilts and bags as he has detailed all the problem spots and how to deal with them.

Thanks guys, a lot of great info here.

The zipper is 3/4 length so I'll have to unseam a little, which means i might as well go into the foot box. Also there is a seam opposite of the zipper so I'll most likely completely remove the zipper and replace it like you said, that's a great idea!

I don't want to go with a quilt though, I sleep sitting completely still so a sleeping bag works great for me and I think it traps a lot of heat.

As for the reactor, depending upon what kind of performance I get out of the overfilled bag I might ditch it down the road but for the meantime it will be nice to keep as a backup in case I get cold in the middle of the night.

Anyways, thanks a lot guys, I really appreciate it. when I get the down and some time to work on this I'll post progress!

I filled my ‘la fayette’ (Valandré) with a extra 100 gram down (3 oz)
I used
this homemade gear
Then I blow the down into the bag with my breath