Im using the same gun in an uncovered corretto and I find it really good to control the ramp. I usually start it off at about 300C on full fan and gradually increase it to around 500C to achieve first crack at about the 13 min mark and second crack around 6 mins later.
I dont know about getting a slow start as it always goes to about 21-22 deg/min and I havent tried to change this. However, the ramp to first crack is a straight line @ 12 deg/min with the control you get from this gun.
I would be interested to know what the difference is with maybe a constant ramp from load to first crack. I would imagine you would have to start and maintain about 15 deg/min to achieve this.
I am more than happy with the results in the cup but we are always open to tweaking our methods. Hope to hear more of your exploits and welcome to the Bosch club.