You do NOT have the option to double down any more with a large bet than a small bet. You double the same hands. You lose the same hands. The EV is unchanged.

EV is negative.
The bet is positive.
The win/loss is the EV*bet
A positive times a negative is a negative. Period.

But, feel free to be one of the milions over the last two centuries that have played progressions in casinos with this odd concept that merely changing the betting pattern without any change to EV will magically allow you to beat the house.