I'd echo what Kim says - particularly that of glue choice when glueing plastics.
Polyprop is notoriously difficult (but not impossible) to glue.
I had good results with Techbond 261 when using correx to improve the hairodynamics of The Red Baron. Important thing was getting everything in place quickly before the glue could cool (which is probably another argument for a higher-power gun).
You may've seen the tool bottle from my Van Nic
It's had a ~20mm extension added to one end, which means a bit more storage, and I don't need to have fingers as long as Gollum's, as there is no bottom to this bottle.
That was done by roughing up the mating surfaces, coating them in RS's Polyolefin Primer and running in some very thin cyanoacrylate.
It has held intact since 2008.
No HMG was involved.