Sorry to hear you ran into a fit problem. I like the ACME fuseholder and I don't mind opening the hole size to fit it, but I understand this may not work for everyone. The fuseholder hole diameter on the DNA-1 is 1/2" with 2 flat sides to take advantage of the anti-rotation feature common to many holders. I often use a smaller fuseholder designed for 5x20mm fuses in other projects, and it has a 1/2" dia. body...but it does not have the flat sides so you would still have to file the hole out to fit. If you would like to try, you can get the part from Mouser.com - part no. 441-R3-12-GRX. Of course you will also have to get an 8A slow-blow fuse in the 5x20mm size. We don't have Radio Shack any more, but if you have any electronics parts store in your area you can take a look at what they have to offer.
I hope this helps - let me know if you have any trouble.
Best regards,
Steve McCormack
SMc Audio