Martacus wrote:After several months of frustration with consistently sour shots...

Sour shots are due to low temperature. A bottomless PF will not help one iota. Crema that is consistently light is an indication of low brew temp.

Can you post a photo of a shot pulled in a clear glass?

My favourite bottomless portafilter is the factory cut/rechromed model Great Infusions sells for $58.99. I prefer when they're cut this way because you get a better view with a regular double basket, and it looks a lot prettier when it's re-chromed.

My own attempt at making a bottomless portafilter is pretty ugly. I got a hole saw and used a drill press, but there was enough chatter that the hole came out very ugly. Didn't help that the dowel I used to guide the centre hole was too long, and was rubbing on the wood I screwed the PF to the whole time, enough to burn a hole. I'm going to clean it up with my Dremel whenever I can find it in the heaps of boxes in the basement (home renovations...).

Here's the process (with photos) that I used a few years back:
http://www.coffeegeek.com/forums/espresso/general/273511

Worked out nicely.

Brad