I completely agree! Take nine of those 10 contracts and just let them sit in your T-bills margin acct. Trade one contract.
If you are trading mechanically, or if you have a good sense for some of the statistics of your trading style based on your historical trades, compare your average trade with slippage/costs of two or four ticks on the futures ($20 or $40). These things are liquid, and they are also volatile.
If your trading style dictates that you will hit the bid or offer to close up a trade quickly (that is, exit or enter on a market order) rather than trying "limit in" you will pay up the spread as well as see some slippage, depending on how fast you are. Figure some costs for paying the spread and a small slippage.
If your average trade is two points $40 or so, then you will probably lose money slowly, if you are entering with market orders. If you are limiting in, then your slippage will be less, but you'll probably see some if you have to hit the bid or offer to get out.
The upside to trading for small moves is that you'll keep your losers small. Once you become proficient and successful in your style, your drawdowns will be lower. Certainly, the liquidity in the ES or NQ will support a 10 contract order.
On the other hand, if you are playing for bigger average trades, you'll have more margin for error in your order placement and any systems problems that may come up (internet connection, charting, etc.). By the same token, you'll have to see higher drawdowns to catch those 10 point moves.
If you are trading mechanically, you are probably looking at the tradeoff between a high win % with a small avg trade versus a lower win % with a higher avg trade.
Either way, walk into this futures market, don't run. It can be very lucrative, but also very dangerous to your equity.