I race in Cross Country MTB races as well as train on tracks that are very similar to racecourses ie lots of climbing, technical decents and some flats as well, and all offroad. Anyway there is very little, usually no places suitable to pedal to speeds where you need the big ring (40 kph+). In ALL my MTB life so far I only use the big ring in order to do some top speed runs and that was on road. Hence the big ring promptly came off today, the added benefit being the extra clearance over logs. Bear in mind my rings are 22-32-44 so thats where misunderstanding comes from, your big ring is only 36 teeth. If you do not use granny at all, take it off. I did the same but with my big ring because in both our cases they are just a useless weight. If you're worried about chain falling off look ingto ways to incrase tension in your chain but honestly you should be fine.
I started thinking more though. Of the racing I have done so far, 2 were completely granny ring tracks, one was middle ring flat track, and other two were granny with one flat for a middle ring. In other words hardly any front ring changing. Hence I took off my front derailleur and shifter. THat saves 500 gm. Form now on, on my sighting lap at the race I'll establish whether I need to shift rings in lap and decide whether to run a front derailleur. I run SRAM chains with powerlink, so the whole 'removing derailleur and shifter' procedure takes about 5 mins with only 5 mm allen key. Whether you can take advantage of this depends largely on the type of tracks you race on, but here in Melbourne, Australia tracks seem to have heaps of climbing and little flats so it will work for me. I may not be the strongest rider (yet), but I know my engineering. It's cause I am one!!!