Yes, as is pointed out above, you can achieve this effect by doubling the tempo (increase by 100%), and then reducing tempo by 50% on the next bar.
You can do this for any MIDI style, and all you need is an expanded version of the style.
You can easily make the expanded style, via a menu command in the StyleMaker (this was introduced about 3 years ago). This works for any MIDI style (not for RealTracks styles though)
For example, if you have MyStyle, and you want an expanded version of it:
1. Open the stylemaker (Ctrl-Shift-F9 or press the StyleMaker button
2. Choose Stylemaker Menu Option Style-Expand Style
- that's it, you then save the style as MyStyleX or whatever.
Then, on any bar that you want 8 chords,
1. change to MyStyleX
2. Increase tempo by 100%
on the next bar
1. Change style back to MyStyle
2. Decrease tempo by 50%
(this only works for MIDI style)