Just leave the top off. Add small indivdual heatsinks to the top of the chips. It allows a better airflow leabing it open. The air flow fro  the fan os pretty totally redticted due to the pcb. Leaving the top off also allows you to add a heat sink to the voltage regs. There is only. The top of the chips toucjing the heatsink. Really for mini g scrypt is it needed a smaller one or ones would be better. Remember these where desgined wattage and heat wise for the sha or dual mining mode.