How to improve cavity size

Hi all,

Baked a wholemeal/wholewheat loaf with following recipe;

Wholemeal/wholewheat
Ingredients:        Loaf 500g    Crust - medium

hot water            1 cup (45deg C)
yeast            2 teaspoons
sugar            3 tablespoons
canola oil            1/4 cup
salt                1 teaspoon
wholewheat flour (stoneground)    408 g
yogurt, strawberry        45g
gluten                3 tsp

Directions:
1    Put hot water, yeast and sugar in a plastic container allowing them to stand 15 minutes. Yeast foams.
Photo: foam
http://ubuntuone.com/1i5YE7aYhRYMYHfyMZ3KWi

2    Add the foam and remaining ingredients to the baking pan
3    Use wholewheat cycle

Total cycle time 4:30 hrs
Preheating :0:30 hrs
Kneading time, total 0:34 hrs
1st kneading (slow) 0:02 hrs
2nd kneading (fast) 0:28 hrs
Rise, 1st 0:45 hrs
3rd kneading (fast) 15 seconds
Rise, 2nd 0:35 hrs
4th kneading (fast) 15 seconds
Rise, 3rd 1:20 hrs
Baking 0:45 hrs

A nice loaf baked with tender and crispy crust and very soft bread similar to white bread.

Wholewheat loaf
http://ubuntuone.com/7B8eJWgMlW7kjtc7DVVYdy

wholemeal slices
http://ubuntuone.com/0bSvWX1EgK8u05tJP8qt4X

However I'm not satisfied with its texture, cavities smaller.

Can I add more yeast making bigger cavities.  OR are there any other solutions.  TIA

satimis