ABS Cement is great stuff if you do not ever want the pieces coming apart...it literally fuses the two pieces of plastic together. I have used it in certain places, but very sparingly. E-6000 is absolutely your friend because you can get it off any plastic pieces with a little work and if you need to separate a piece later, an razor will do the job. I have never had a melting problem and I have trooped it in 105 degree weather (not recommended).
As for the forearm to bicep, as Todd indicated, it will blend to your under suit.