On the SLA front, it depends on how competitive you want the robot to be. The Scot-Bots use an SLA, the ones we use for demo's use 2 SLAs and we've run them for 3-4 days without needing to charge them. Obviously if you're looking to win the UK Champs with it then the extra weight can be better used elsewhere but if you just want a robot that you can throw into the arena without too much work between fights then they're not too bad.

SLA + Wheelchair motor is pretty much the entirity of your weight though , so if you're going down that line then you'd want something lighter. Jamie's had a battle getting Onyx in weight and using a Li-Po it scrapes in at the weight limit (sometimes). Like I said before though, if you're not entering it into the UK Champs if its a few grams over weight it won't matter too much, especially if you have all of the stuff you want to use sitting there already.