I appreciate where you are coming from Fugazsy, but it all depends on perspectives.
Let's take your example, you put in $20k, then made an additional $40k, then you pulled out your initial investment, then effectively, you are playing with winnings, rather than any of your initial investment.
Yes you could stick just $20k, and take 2.5% risk, thus it is the same as effectively going in the same as 0.5% with a $100k, but what happens, if one day you see a peach of a trade, and want to go in a little heavier.
Say 3% risk on $100k, to get the same on $20k you are risking 15% 😱, and if the unexpected proverbial shhhh hits the fan, then you could be getting a margin call, and effectively losing the $20k invested.
So is it better to have a bit of breathing room, where a dent can be recovered, or play tight, and effectively have a blown account.
I hope that makes sense, or more importantly, understand my perspective.
Best
John.