I apologize for not getting on here sooner, I was moving my daughter back to Indiana from North Carolina......thank god that's done.
I'm not familiar with Aspire, but I'm sure they have a similar function to Photoshop and other photo editing software. In PS they have an option called "blur". What I do is always have a small white border around my entire picture, this seems to help the software set a starting depth. Then I hit "select all" so that everything in the picture is affected, then into "filter", then go to "blur". I choose gaussian blur and set it depending on the picture being blurred (your choice), normally between 2 - 4 for most. This blur has the effect of changing the borders of all edges by blurring them, causing the ipicture software to see different depths. The end effect is a curving of the edges. For carving, this means as you go from the white border to the cutting depths, the machined gives you a rounded edge going down to the cutting depth (instead of immediately plunging to the full depth). So it might take two or three passes to get down to the full carving depth instead of trying to do it on the first one, when it is carving into a wall, rather than just trimming off one side on further passes. This rounding has the effect of not causing so much sideloading on your spindle motor.
Note that doing it the way I speak about above with round over all of your carving, it might take out some sharp details that you prefer to keep. If so, then instead of "Select All" you need to highlight just those components that you want to blur. More tedious, but it works. It all takes some playing around to get used to using the blur to get the most out of your pictures.
I also never carve any piece deeper than .25" or 6mm. I have yet to try a double pass for a deeper end result, so I can't really address that.
Bix, here is a poor example of what I'm trying to accomplish with the blur function. Note that there is a white border around the piece, this is for the reasons mentioned before and the fact that since the bit isn't carving this area and I'm cutting it off with a scroll saw anyway, I'm saving wear on the bit.
Note that without the blur, the cut would be a plunge style straight down to the black depth. With the blur, you can see more of a slight curve that the bit follows over several passes to get down to the final depth....reducing sideloading on the spindle motor shaft, especially during that first cut.