Without having access to a database, I will hazard a guess and say that the results would be pretty much the same either way. You would return 85-90% of your money.
To use a staking system you first must have found the best value possible.

There was a similar discussion on another thread comparing taking 1,2,7,8 versus 3,4,5,6 on the dogs.
The first option won much more frequently than the latter, yet returned less to the pocket.

Odds versus Evens however will not have a difference in frequency of wins.
1 vs 8
7 vs 2
3 vs 6
5 vs 4
These numbers are all comparible and added will give you the same return.
You are not increasing your value at all.
Maybe look at backing the 4 longest price dogs in the field, dutch them and stake them.
I personally would only ever consider a staking plan for a win bet on either the 4 or the 5, as I feel they give the best value.

Somebody with a database might come along and prove me wrong though.....