Is there some way to tell Realtracks to start at "certain offset position" at specific bar?

My problem is that I'm trying to create backing track with acoustic guitar for a long (~5min) song. Style should be just simple waltz strumming.

When I generate the track it always has strange rhythmic changes at some bar, either right at the beginning of the song or X bars later. When I happen to generate version which starts like it should, I'd like too keep that "beat" all the time, which means that I'd like to loop that ~4 bar section over and over again without any variation.

I already tried "force track to simple arrangement", but that made it "too simple" by taking off the rhythm and changing guitar to picking slow style, while I'd like to have just a solid strumming. Is this possible?

Additionally sometimes guitar chords get played from higher position. Is there a way to force playing to lower neck positions, so that the sound doesn't become "too thin"?