When It is possible!
I use clamps of one form or another. That said, I do use tape, but, with a twist. When I use tape I make a concerted effort to be sure the edges have wet glue on them before taping. That way I can draw them together tightly and the glue has had time to react with the plastic so it won't destroy the tape at the joint. Otherwise I wrap the fuselage with strips of polethlylene bags then tape over the strips. The glue won't stick to the polyethylene material.
There is a universal problem most, I am sure, have faced. Good old Scotch Magic Mending Tape. Best tape I have ever found for initial construction. BUT, don't get to close with the Tamiya liquid glues or Testors either. It will run under the tape making and imprint OR the chemicals contained within will just eat through the tape!
Rubber bands can be used, how you use them is the trick. Same with clamps. I actually haven't found a good, non marring, clamp for odd or tapered surfaces. Yes you can use "GatorClips! But beware! The finer finished chromed metal, plastic dipped ones don't grip tapered surfaces that well, They will slide.
There are much cheaper ones and I can't really tell you where to get them, I have found them at Flea Markets, Train Shows and generic Hardware stores and even Wal-Mart at one time. They are cheaply made, Aluminum? and have very sharp teeth. Now here's the thing You bend the wire connection arm out of the way(Do Not remove it!) then the jaws open wide.The teeth may make teensy divots, But it's rare as long as you don't force them.
On the other side you bend up the finger pad a little, the jaws will really open wide. Clamps, Wedges etc. Not everyone has a vice in which you can use Rubber Wedges. I used to use a bench vise on a Carpenters bench. Then for holding planks in place on hulls various sized Rubber door stops. Archaic, Yes, But it worked. I have NOT had any luck with those " Helping Hands" tools.
Overall I have found that a little surgery in unseen spots usually works well. Then it all comes together. Oh, Before I run off. I found this by accident. I had a B-29, Monogram's monster. The Fuselage was badly curved on both halves. I fastened both sides to perfectly smoothh Pieces of Tempered glass on a Countertop in my shop. This was placed in a cookie sheet, then after blocking what I could and taping it down with Duct tape, I poured boiling water on it! Both parts fit perfect after that. I do not recommend this though. You can splash dangerously hot water where you don't want it.