The GSG conversion kit was not the problem you are correct. The issues were with the barrel conversion and rear drum sight.
Also fitting a red dot using a claw type mount varied with the brand of mount which also carried over to the aftermarket cheap stocks and handguards that "almost" fit right. Gaps here,rattles there, sights that ended up being there just for looks as the didn't align right.
However I also do want to point out that the ingenuity of some members here to adapt and create parts is amazing!!
Well comes down to personal preference, research, ability, and want.
I love the GSG16, but after shooting a MP5 in Vegas I never shook that fix.
Have I spent too much on my GSG16 in mods, yes. Any regrets nope! I have saved lots not doing the wing/beer thing and have something I love shooting.
My buddy just picked up a green GSG16, so I brought my modded GSG16 over to compare. In stock form it felt very light and plasticy. Mine is heavier, more solid, and IMO just feels like it should.
You comments about builds not working out, are not accurate if you do your homework and choose wisely. I used an 3D printed rail that allowed me to use a beefier scope clamp, the stock was dremelled out and is tight, front grip was bedded and is tight, rear sight block was built up with JB Weld and fitted to the rear sight base. The metal cocking tube adds to the overall build and correct sighting HK experience.
The plastic 20mm top rail with the 2 brass inserts is not robust for optics. So I have no regrets over my 6 month patient proper build. And yes the barrel from Dlask is awesome, as the faux suppressor and fragile rear sling stock just doesn't go well with my other toys.
Not the best build but it reminds of my MP5 experience way more.

Each to his own I guess.
With the stock barrel:
How it started my simple bolt ons:
I learned from others here, that helped with my build, as well my buddy is a machinists and I like tinkering, so this was an easy build compared to some others. I did the same type of build on my 10/22 shorty, I love both when shooting reactive metal paddles.
