Have you tried the latest CamBam 0.9.8 release? (Release 'i' is the latest).
CamBam CNC Software - Downloads
This has a new feature where you can set the LeadIn move to spiral then set the spiral angle to 0 degrees. CamBam will then use the depth increment value to control the pitch of the lead in so that it does 1 spiral per depth increment.
This produces a very nice, efficient toolpath that gently spirals all the way to the target depth then does another cleanup pass at full depth.
I use this method all the time now...it works well.
The downside is that you will do at least 2 circuits around your parts rather than 1 (which it sounds like you are doing).
This might actually be a good thing. If your machine is not that rigid this will reduce the cutting forces so you might find the gap between start and end is reduced. The spiral lead in will also overcut the start point which should cut away the residual ridge.
I hope this helps and good luck!