I'm trying to bake a simple pan loaf of bread with 50% whole wheat flour, 25% whole white flour, and 25% rye flour.  I've tried various things to try to get a nice rise and open crumb but every time I bake it the loaf seems to deflate in the oven.  It loses height and pulls away from the side of the pan.  I've tried rising longer, rising less, adding gluten, increasing hydration, hand kneading, folding, machine kneading, rising in the oven with the light on, rising at room temp (~71*), etc.  Any thoughts on what could be going wrong? 

Here is what I'm doing that seemed to work the best:

250g whole white starter at 100% hydration Montana Prarie Gold

235g bottled spring water

250g whole wheat flour King Arthur

125g Rye Hodgson Mill

1 Tbs of vital wheat gluten

2 tsp salt

Mix together all ingredients except salt with a wooden spoon and let sit for 10 mins covered with plastic wrap.  Knead on 2-4 in a kitchenaid for 8-10 min.  Shape into a ball to rest for 15 min in a bowl sprayed with olive oil spray covered with plastic wrap.  Knead in salt to mix it into the dough.  Shape into a ball and rest 1.5 hrs in a bowl sprayed with olive oil spray and cover with plastic wrap.

Shape into a loaf and proof 2.5 hrs in a greased loaf pan in a shoe box.  The dough was about 1.5 inches above the 9x5 loaf pan.

Place in a preheated 375° oven for 45 mins.  Internal temp reached 207°.  The bread deflated to about the level of the pan....maybe a little above.

Any help would greatly be appreciated.

Thanks.