as you know i think the IMS B70 2T h26.5 is easily the best basket for updosing in the LONDINIUM lever espresso machines
some have remarked that it is a fine basket, but it is ridged, which is true
i purchased the B70 2T h28.5 IMS basket some time ago but it sits too close to the bottom of the naked PF, resulting in the coffee bridging the gap to the body of the portafilter and flowing out along the bottom of the wenge handle and dropping uncermoniously on the kitchen floor (it works perfectly in a conventional PF holder)
so i found the IMS basket i was looking for here http://www.espressoservices.co.uk/ims_gaggia_double_basket_16_22.html
it is ridgeless, but has a slightly small diameter rolled rim, 68mm instead of 70
i will report back as soon as it arrives, but as long as the crema clears the bottom of the L1 naked PF i expect it to be a winner