Collecting 0.0488% every eight hours, a basis trade meets a 7.95% rebound day
Should the basis trader keep the spot-and-perpetual-short position at full size for the funding, or cut it so the short leg's margin survives a day like Wednesday's 7.95% rise?
The market facts are real; the decision maker is illustrative.
The week and the position
In the week of 3 May 2021, BTC closed 2.94% higher at 58,240.84, 9.81% below its 52-week high, with a 12.48% range from 52,900 to 59,500. Tuesday fell 6.94%, including a -3.28% hour, and Wednesday then gained 7.95%. Perpetual funding averaged 0.0488% per eight hours, peaking at 0.0935% and bottoming at 0.0117%. An illustrative basis trader holds spot BTC and an equal short in the perpetual, earning that funding while carrying margin risk only on the short leg.
Judgment
Funding of 0.0488% per eight hours is real income, but it is paid on a short leg that must meet Wednesday's 7.95% rise on its own margin before the position's hedge pays off. Keep the trade, but size the short so its margin absorbs a full day move equal to Wednesday's inside the week's 12.48% range, and hold the spot leg liquid enough to post that margin quickly. Treat funding as carry that ranged from 0.0935% to 0.0117% within one week, not as a fixed yield.
What would change it
If funding falls towards its 0.0117% weekly low or turns negative, the income no longer justifies the margin cost and the position should be closed. If the venue allows the spot holding to count as margin for the short, the size limit can be relaxed.
What sets this case apart
The risk here is margin timing on the short leg across a two-sided week, not the direction of BTC or the size of the weekly gain.