Is a complex exchange transaction involving unequal weights or measures permissible as a means to effect a trade at an unfavorable rate?

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Transactions designed as legal devices, such as where one possessing ten sound coins borrows fifteen mixed coins from another, and they subsequently agree to trade the sound coins for the mixed ones at an unequal rate (or selling sound coins for an equal number of mixed ones and gifting the difference, or using the difference to purchase a low-value item), are fundamentally forbidden and considered foul. This prohibition extends to any transaction where a loan, overpricing of goods sold, or underpricing of goods bought is used as a device to receive compensation for a loan (Riba). Malik supported this prohibition.