I don't want a fully enclosed device and I'd like to keep the weight down.
But you also want the chain to stay on over the "bumpy stuff" right?
This really is the new "what tyres" thread, gets asked at least 4 times a day!
Anyway... The age old adage of "cheap, light, actually works, pick two" never applied more than with chain devices. Everyone wants the moon on a stick these days, but ask yourself this... How many downhillers do you see running top only guides on their bikes...? Pause for thought there!
The reason for that is cos if you want the chain to stay on all the time, no matter what, you need to get a good chain device with a top and bottom guide and it needs to be setup correctly. The number of people, just like tinsy up there, that piss about with a Heath Robinson approach cos they're too stingy to buy a proper chain device (yet will buy XTR rear mech, carbon bars etc.), and then give up on 1x as a "fad" or "too niche to be any good" because it didn't work properly for them.
Buy an MRP Lopes SL, G2 Mini, an E13 LG1, a Straitline silent guide, or any other similar device, and you'll not regret it! They're not cheap, but they bloody well work!
By all means though, if you're happy with your chain falling off a few times every ride/race then don't let me stop you from being cheap...