"...people use to drill holes in the rubber part of the cone to try to make them more compliant."

Sounds like bodge territory to me. To start, drilling rubber is very difficult. To drill a cone evenly, you'd have to remove it - easier to put a fresh one in at that point. Drilling holes where they shouldn't be would allow the ingress of water and dirt (and the cone would act as bellows to pull stuff in). An already aged rubber might fatigue break or collapse more. I could see it done on a fresh cone to get specific handling, though Moulton had the original cone design dialed in for the original Mini. When he designed the Smooth-a-Ride cone, he changed the inner and outer profiles as well as the height. It came as a set, with adjustable trumpets and selected shocks to suit the different spring characteristics.

When I installed mine, the adjustable trumpets were wound just about all the way in until the new, taller cones settled in, which from what I read at the time might take a few weeks. My mini is not a full time daily driver, so after several years it came down to close to proper ride height. I still have not had to re-adjust them. One benefit of having adjustable trumpets is you can balance the weight distribution.

Dan, people use to drill holes in the rubber part of the cone to try to make them more compliant.

 

 

Does anyone know how long a new cones lasts these days. I've been running  LSS springs from Japan as my mini is my only car and a daily driver. I can't take the jitteriness. 

Yep. Old suspension cones collapse and get as hard as hockey pucks. In the attached photo, the nearest is one of my old cones, original to the car. The middle one is a standard new one and he farthest one is a later design (by the original designer) called "Smooth-a-Ride" which provides a slightly softer, more compliant ride when lightly loaded but firms up quickly when loaded as when cornering.

My guess is that you need new cones rather than shocks. The cones are hard as rocks and sagged.

https://usa.minisport.com/kyb55201kit-kyb-gas-a-just-set-of-4-mini-shock-absorbers.html

Where can I get these shocks?  Look out of stock.

Don't know what BOC is but any of the upgraded shocks are good. I run KYB Gas-A-Just shocks for years with no problems. I drive sorta hard and cruise around town too and the ride is fine for both. Check with Mike with Mini Sport USA to see what he may have available. https://usa.minisport.com/

Recommendations for 1993 Mini BOC shocks?  Currently running originals that feel beyond expired.