Yes, slower setting poxy tends to be stronger and tends to "sink in" to the wood/balsa better, plus it gives you more work time. Ever notice how 5 minute epoxy gets kinda stringy after a minute or so?

For joining wings and tail surfaces, I recomend that you use a slower epoxy (like 30 minute) so you have time to check, recheck and check again that the pieces are together straight and proper.

Happy building.