I also noticed something else. If ETH goes up 4X you double your money. So in that case it is half the gains. However, consider the case where ETH goes 4X again, after having already done a 4X.
This now means ETH is up 16X, but you will only make a 4X on your money. So you don't make half the gains in that case, you make 25% of the gains.
In fact, you will always make the square root of the real gains. If Eth goes up 10X you will make approximately 3.16 times your money.
3.16^2 = 10.
When you add this to the fact you need to hold in DAI the USD amount of your ETH. The loss on an ETH 10X is HUGE. So my other comment is wrong, I was assuming you would make half the gains with your ETH.
This also means that for gains less than 4X, you make more than half the money. For example, for a 3X in ETH, you would make 1.73 times your money because 1.73^2 = 3.
Making half the gains would mean 1.5 times your money, but you make more in that case.
So, in short, the bigger the difference in price, the larger the rate of loss becomes for the same change in percentage gains.