Top Quilt mod question

[clutch146]

I recently bought a small DIY top quilt for the price of the down in it and was planning on extracting the down to make my own top quilt. However, due to time constraints, I'm thinking about just modifying this quilt to fit me better. It is 66 inches long, 40 inches wide at the head, and 32 inches wide at the feet (the foot end was sewn together, but I've already ripped that seam), so I'm left with a trapezoidal down blanket at this point.

My plan is to add a rectangular piece to the foot end to extend the foot end width, and a circular piece at the very end to close it all up. Here's a (very) rough idea (sorry for the early morning ms paint puke). In these pics, blue is the existing inner shell, gray is the existing outer shell, red is the new rectangular piece, yellow is the new circular piece, and green dashes mark sew points:
bottom.png
view from bottom
foot_end.png
view from foot end
sew_pattern.png
sew pattern

I tested this pattern out with bed sheets, and it seems to give me the extra room I'll need to make it work. My question is what material and insulation should I use for the add-on pieces? Is it worth it to get extra down to complete this (I'd probably need another couple ounces)? Or, since my feet will be laying on the new rectangular piece, would I be compressing that down rendering it ineffective? Should I go with a small amount of climashield instead? Insultex?

A little additional info... I'm 5'7" 185lbs, I sleep pretty warm, I'm looking at taking this down to 20 degrees, and I have a 20 degree underquilt that comes down to the top of my ankles. Thanks in advance!

[Scotty Von Porkchop]

I've got big feet so I also added a piece to make for a roomier quilt, I thought that adding a round and a rectangular piece was unnecessarily complex and didn't achieve much so just added a rectangle to the bottom.

DSC_0895.jpg

[clutch146]

Maybe I'll swap out the circular end for a more rectangular one - looks easier to sew. However, I will have to have the rectangular piece on the bottom to widen the foot box - too cramped in there for my legs at only a 32 inch circumference. So how best to insulate the additions?

[e_2]

buy a 3 oz. pack of down from http://thru-hiker.com/materials/insulation.php to fill the additional piece. The 800 fill power down is treated to be water-resistant... might be a good thing to help keep the footbox from getting foot-scented. Also... you won't use all 3 ounces. I'm guessing it will take around one ounce to get to the temperature rating you are going for.