Hi
I would offer the following…
1. I have not experienced painted parts not glueing together. Metal parts I use superglue plastic uhu or any plastic glue…
2. I used to glue the exiting base down then base over it…but nowdays I tend to cut away from the Base if possible and re- base onto clear plastic sheet. You can see some pictures of our stuff at Glasgow Warhog blog. The earlier posts were based then flocked etc. but the newer ones are on clear plastic. My problem is I don’t like re- basing for different games…street , sand, grass but I am being picky.
Some people don’t mind the colour miss match. I like the idea of the base disappearing into the ground. So I use a two part epoxy to glue the base to the figure with clothes pegs to support them during the cure. This means the base can be really thin.
It’s all personal choice really…I your happy with the result go for it.
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