Betting a small percentage of bankroll should in theory mean you never run out of funds. Instead you should seek to bet proportionally. Secondly, staking such uneven amounts means you may not be making the most of your wins. You've just bet a whopping 36% of your overall bank in an unproportionate way.
If as an example you have £500 in your betting bank, it arguably makes little sense to place two bets of say, £70 and £110.
Pros & Cons of a Proportional Betting strategy