Bernie, I just want to share what I have done when I've wanted to add a 'solo' section in a SMF ...
Let's say the first verse is A to B, the bridge/chorus is C to D, and the last verse is E to F, with F being the ending of the SMF.
If I want to perform a solo over A to B and then go back to the bridge/chorus, I would COPY A through F, and insert it where I want it. I would then eliminate any note data and other info from the track I want to solo on.
Note: As Steve A may have alluded to, what must be taken into consideration when inserting A to F is how many bars before the ending it must be inserted so that you don't play the ending before starting your solo at A.
Copying A through F saves all the end of the SMF data so the song will end as it should.
Obviously, this extends the song quite a bit, but it is in line with how songs are usually performed by band.

If I were looking to only add 8 or 16 bars from A to B, let's say after the bridge, figuring that I need the midi data (bass line, chord changes etc. for those bars), I would COPY the bars I want, insert them after the bridge, and remove the notes,etc, I do not need from the bars I want to play over.

There may be some trial and error involved in order to achieve the proper transition into and out of the solo part.

I know this sounds confusing, but I hope it helps.

Any questions feel free to ask.