The red LED needs about 10V less than the blue/green so it might need a resistor to absorb the extra volts.

10V@300mA = 33 Ohms, although it will need a large wattage.

Something like this should be enough: http://www.ebay.com/itm/271109598315

I'm trying to avoid the use of resistors to limit the current directly to the led because it's a waste of power. I prefer (if possible) to limit the current trough the MOSFET.

> The red LED needs about 10V less than the blue/green so it might need a resistor to absorb the extra volts.

*Each* LED needs a resistor to limit current, but yes, the red LED needs a different value from the rest.

As for taller heatsinks, look at these...

http://www.ebay.com/itm/Heat-Sink-for-20W-30W-50W-LED-/380534842067?pt=LH_DefaultDomain_2&hash=item5899a4e2d3

http://www.ebay.com/itm/20W-30W-Led-Light-Heatsink-With-FAN-Aluminium-Cooling-For-20W-30W-Led-12V-/190785568355?pt=LH_DefaultDomain_0&hash=item2c6bb4be63

The first one is perfect, tall but the base is small, it would fit. The second one there is no way I could fit it in the spot light.

Speaking about the voltage of the LEDs, I found something interesting.

`30W:`

Color: RGB

DC Forward Voltage (VF): Red 22-24V, Green 32-34V, Blue 32-34V

DC Forward current (IF): 300MA

Out put Lumens: Red 400-500LM, Green 600-800LM, Blue 200-300LM

Wave Length : Red 620-625nm , Green 515-520nm, Blue 455-460nm

Beam Angel: 140 degrees

Life span: >50,000 hours

50W:

Color: RGB

DC Forward Voltage (VF): Red 22-24V, Greed 32-34V, Blue32-34V

DC Forward current (IF): 300MA

Out put Lumens: Red 400-500LM, Green 600-800LM, Blue 200-300LM

Wave Length : Red 620-625nm , Green 515-520nm, Blue 455-460nm

Beam Angel: 160 degrees

Life span: >50,000 hours

The specs for 50w and 30w are the same but the layout of the array of LEDs is completly diferent!! (see the attachment)

In the 30w version , for every color, there is 1 row of 10 leds and in the 50w version you will see 2 rows of 8 led.

Since the 10w version is 3 led per row and the 20w is exactly doble and the voltages match, it easy to figure out the voltage for the 50w version.

`10W:`

Color: RGB

DC Forward Voltage (VF): Red 6-8V, Greed 9-12V, Blue 9-12V

DC Forward current (IF): 300MA

Out put Lumens: Red 120-150LM, Green 200-300LM, Blue 70-100LM

Wave Length : Red 620-625nm , Green 515-520nm, Blue 455-460nm

Beam Angel: 140 degrees

Life span: >50,000 hours

20W:

Color: RGB

DC Forward Voltage (VF): Red 13-15V, Greed 18-20V, Blue 18-20V

DC Forward current (IF): 600MA

Out put Lumens: Red 260-300LM, Green 400-600LM, Blue 150-200LM

Wave Length : Red 620-625nm , Green 515-520nm, Blue 455-460nm

Beam Angel: 140 degrees

Life span: >50,000 hours

If the 10w red is 6-8v and contains 3 LEDs then 7/3= 2.4v per LED. Therefore the 50w version,wich contains 8 led (in each row) will be 19.2v.

Applying the same for the other 2 colors we will have than the green and blue are 28v each.

I don't know any other way to find the voltage safely without destroying the LEDs.