[quote name='stevie' timestamp='1472989218' post='3125765']
I agree with those who have replied already - cutting up an expensive cabinet will reduce its resale value and might not give you the result you're after.
Another option would be a box with a small tweeter that would fit on top of your existing cab(s). Google Greenboy Head Case for the general idea. If you use one of these tweeters: <http://www.bluearan.co.uk/index.php?id=PAUPHT416&browsemode=manufacturer> the whole thing should come in at well under £50 and is likely to sound better than most commercial tweeters. Apart from the box, you'll need a couple of Speakons, some speaker cable, a capacitor, inductor and L-pad.
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That's exactly what I did a few years ago with my G1 Compact. It was a tweeter with a built-in crossover (or didn't need one, piezo?~)
and it added a bit of air and click on the attack. I didn't find it too hissy at all. It was a type used in Trace Elliot's p.a. series of speakers.
Tiny ply box, Speakon, you're away! I just Velcro'd it to the top of my amp.
I've actually got a spare one if you're interested.