Ok, I have done 3 x race meetings so far with the Delta 3-shoe.
Here is the scenario:
I run a GRC RR 06, 50cc BZM 6-port with PHBG20 carb. No other engine porting or other mods have been done. Engine runs up to 15300 rpm with ergal housing and ventlating bell. I am 93kg+ and generally run about 2-3s behind the fastest guy (55kg) at our regular race track (600m), 100km south of Sydney, Australia.
Here is the feedback:
At first bite -

. However, after some heat in them, the bogged down feeling became really noticeable and laptimes went backwards

.
Initally, the clutch was setup to engage around 7800 - 8000 rpm. Careful observation of the wear pattern at this early stage prompted me to adjust the springs to obtain even wear first and then a further change to move the engagement rpm to 8500 rpm. Things improved after this and with the shoes now bedded I have moved the engagment rpm to about 9300 rpm. Laptimes are getting close to what they were with 3-shoe carbon pads.
Heat is still the killer, but clutch life is much better and I will be interested to see what occurs when a new set of shoes is used with the bedded bell. A little more practice should yield equal results to previous laptimes.
My tip is to be patient and setup the pads with care and try to improve bell cooling and you should extend clutch life by about 5 times your usual wear rate.
Conclusion:
I will continue to use the Delta clutch pads due to the extended wear characteristics exhibited

.