I didn't have this problem in by pre- or early-BAR days, that is, over weight models and large amounts of nose weight weren't major issues. When I started in HPR, however, my rocket building style began to change. If I built an MPR model that got too heavy, I could just stick in an 'H'. I soon learned that building with bigger mounts was a good thing and that adapters were my friend. A small HPR too heavy for an 'H'? No problemo, there was always an 'I'.
Well, I no longer fly HPR and for a while rocket obesity didn't seem to be a problem. Maybe because I haven't built that much mid-power stuff. Things turned to the dark side with my F-104 Starfighter. I wanted to fly it on 'G's but by the time I added the required nose weight, it was close to outgrowing the largest available 29mm non-regulated motors. Oh, how I wished for an old G125 single-use. On the field, everyone liked it so much that a volunteer with an H128 appeared. I may still try it on a G reload but am hoping for a new motor in the G125 range.
Then came the Pogo. The bottom end would only accommodate an 18mm motor. The PMC is heavy and by the time the nose weight was designed-in, it was clear that a C6 wasn't going to be enough motor. The rocket weight problem had spread to LPR! Anyway, I have no C5's or an 18mm RMS case so I had to add two 13mm boosters. It actually looks and flies cool despite the loss of 'scale points'. But the handwriting was on the wall.
Now, I suddenly find two LPR models on the bench that are facing the same fate. My X-20 Dyna-Soar carrier and the Goony XL5 are both weight-challenged.
The large fins on the Dyna-Soar and small fins on the plastic Nike fin unit mean that a lot of nose weight will be required. I could drill the balsa cone and fill it with lead shot, but this doesn't bode well for its survival on landing. Even if I stretch it with another length of BT-60, some weight will be required. And IMO, it doesn't look nice stretched. I'm pondering dual chutes and maybe adding the weight in a separate unity below the cone.
The Goony XL5 is also getting up in weight. I haven't formally assessed stability, but added a bunch of lead shot to the nose based on a gut feel from my other XL5 endeavors. This model has gone the way of the Pogo, and that means an 18mm RMS case is on my buy list for next Spring.
So, rocket obesity has spread throughout the Dungeon. Maybe rocket weight just gets harder to lose as one grows older, just like your own weight? Is there hope?