If you want to trade 40 contracts, and will only put up 25k, this means that you can only take a loss of $625 per contract before you run out of money. This is 12.5 points.
The thing is that these days, in only the past month, we have had several gap openings between either the Friday close to Sunday open, or even the 5pm close to 6pm open, that were a good 10 points or so. In these cases, the gap was in complete opposite to the preceding trend.
If price is moving, its highly unlikely that your backer would be hit hard because its fairly easy to liquidate you within a few ticks of your max loss of 12.5 points which your 25k would cover as price approaches that loss. But when the markets close, even for an hour, your 25k might not cover the loss from where it opens, which you can't do anything about.
If this was during the day, I'd say fine, you might find someone crazy enough. Perhaps your strategy scales into a trend, and if you get lucky and catch one and keep adding, you can very quickly build a buffer, but you cannot hold a position like this overnight when the market is closed with such a small buffer.
These days, a nuke might very well go off and the gap open will be much more than your 12.5 points of buffer will allow.