From what I understand, although I have no proof to back it up, so your mileage may vary. You can use your service mode dongle to downgrade to a lower firmware like something in the 2.xx range (anyone have any input on which one?). Exit service mode. Then using the unmodified 3.41 .pup install firmware 3.41.
Absolutely make backups of your ps3 hard drive before you start this proccess!