I used Pspice and LTspice about 12years ago when I was still a student, but the world of management swallowed me up before I could start practising. I have started to dust off my old books to get back into the game. Anyway thanks for all the advice, this exercise gave me some insight into how rusted I became.

Totally agreed, garbage in garbage out.

However, I do appreaite everyones insight regarding this - nice to have a debate with educated oppions for a change :) thanks for that.

The whole Idea behind the question was to see if there are practically approached for not ideal designs. If you worked for a company and your boss says there are 20 LEDs build a light. You can't really say - no I can't it's not sound engineering practice. You will figure out a way to make it work. By adding current balancing circuits, and LED shunt switches for protection the design might work. I do agree that this design will not be used in the new BMW headlights or emergency lights for an aeroplane, but the question is will it physically work, and deduced from this thread, yes it might.

I have been looking around for a nice circuit sim, I guess I will go with circuitlab. I have been using Altium, but in the same breath have been out of the scene for years. Playing catchup atm. The circuit above Is what I mentioned in one of my comments. As you mentioned 'It is not as perfect as 2 independent current sources but may be close enough depending on your specs.' I will also then add a current balancer LM3466 which is quite a usefull little black box.

Thanks for the comment, yes I also do understand the concept of thermal runaway. Having one type of LED makes life easy, well life as a light fixture, but surely there must be a way - there are several high power led lights on the market using different light spectrum LEDs (different V@mA specifications) in S/P combinations or maybe they are driving them below their typical fwd current points, or might even drive them as separate series strings at an undercurrent point. All and all I do agree with all the sentiment that combining them is bad engineering practice - but still :)

Thanks for the feedback I do appreciate it. First off all the heat dissipation throughout the board can be assumed to be linear as I will use an 'infinite size heatsink' for the spice. The option of using a separate CC source will absolutely do the trick, I understand that yes. Let's assume I have one 2000mA source. A simple solution might be to add the R led's in a series chain before the parallel combinations of white only strings, maybe this could work.