Yeah, unless you want to run them at much less than full power, or risk damaging them, using resistors for high power LEDs is not recommended. Its a fine method for small LEDs, though.
The issue is that every LED has a different voltage drop across it, and that drop will vary based on several factors, including temp.
The way to run them is a constant current source. What you can do, is put them in series, as many as practical.
For OEM designs, we run 2 whites in parallel, because we need to run at 9 volts. On a wheeler, Honestly, if the voltage is below 12 volts, then I have other issues..
So, I run 3 whites in series. Then I use an adjustable linear regulator configured to create a constant current source. Cheap and simple.