As Arthes says, in Comitatus, females are allowed in male kit as soldiers. However, we try not to appear in the Living History camp in male gear. It sometimes doesn't work - for example when we were doing the Ad Sigma last year a member of the public saw my (male) name on my shield and was asking about its meaning. I tried to make the conversation very short. Also, if the time between 'arena' shows is short, it's not worth getting changed. I have occasionally been in camp in male kit, but kept my head down, not talked to the public, and been doing something that wouldn't look out of place for a bloke (i.e. gossiping to my mates, while the women do all the work :lol: ).
When doing the male role, we wear helmets (borrowed or owned) which lends a more male look, at least from a distance. Cheek pieces on the helms also help. For some slightly built women, it might be good to wear armour to bulk them out a bit (I don't have that problem!). Lorica segmentata would probably hide a multitude of sins, in that respect :twisted: No armour: baggy tunics are a good idea. I always generously pouch mine over my belt allowing plenty of room around the chest area.
In England, one of the main events organisations, English Heritage, are not keen on women cross-dressing, as it's confusing for the public. At those shows, we certainly can't be seen in male kit wondering around the Living History camp as a matter of course. However, in allowing women into male kit, the group can maximise the number of soldiers doing drill, for example.
If you're female and caught in in male kit at virtually any show, there's only one way the conversation is likely to go! I don't like having the same conversation over and over, and in the Living History camp I am there to to talk about everyday aspects of life in Late Roman Britain.
Comitatus has a large Living History camp, and there are lots of women (dressed as women!) in it. Most of us don't portray high status females - except, appropriately, the Commandant's wife. We all have our specialisms, such as dyeing, weaving, pottery, cooking, etc.
Hope this helps