Jimbon, Shug's DPF is totally hollowed out, I did it (for research purposes only
). If you want to hollow it out, there's a few options and I've done most of them.
Buy a 530x25mm masonry drill off eBay for about £5.
Completely remove your DPF box from the exhaust.
Stand it on its end or in a vice and drill in from the rear end. The 25mm drill will cut you a pretty neat hole all the way thru the core. You'll need the long length to get right thru without a faff. There is a gap, probably around 2" after the DPF core and then the CAT core starts.
You can either go thru the CaT or leave it in, mine is in, I don't feel any power loss and I feel slightly less guilty.
Or you can drill a couple of holes with the drill so there's plenty of room for deadly pollutants to escape.
Now if you only drill a couple of bores thru, then anyone who gives the DPF box a knock to see if it's been emptied, will think it's all intact. If you carry on to drill and smash the dpf internals with a crow bar, it will be a hollow knock if someone investigates it.
Or you could leave your DPF intact and buy a straight thru pipe replacement, so you've always got the option of refitting when/if the rules get even stricter. Jabawokjay and me have straight thru pipes for sale, buy his first, he's been flogging it longer.
Or you could do what Fixitsan does in his youtube vid and just drill a few 10mm holes about 15-20mm into the dpf. Apparently it's at the back where the ventricles are smaller thus trapping more death vapour. You'd still need a dongle/dpf delete for this.
Personally I don't see the point in drilling out the CAT part and I think in hindsight I'd try and find a drill bit just a bit narrower than the exhaust pipe and drill a nice clean bore right thru the dpf leaving the CaT intact.