Oh goodness me, what a question. I got the setup ready made from Steve at Fosworks. I think the resistance is about as big as you may be able to get, tis the grey/light coloured thing. It does get very hot if there is a lot of juice still in the battery.Very useful advice, Jon. Thank you for sharing it. What size of resistor did you use?
I mounted the vero board on some ply using araldite and the board is normally held aloft on crock clips. Certainly the battery getting warm can be an issue so I set an egg timer for 4 minutes to look at it to see how the battery reduction is going. The lamp gives a clue going out when fully flat and dimmer as power declines.That is a 6.8 Ohm resistor, but the main criterion is the power it can dissipate..
You can use something like a 21W car brake light bulb.
Whatever you use, it must be supported in free-air. - It will get warm (minimum) but more likely HOT!
Don't leave it unattended, and check the battery pack is not getting more than warm to the touch.
PhilP