I think the risk of personal injury is minimal so - long as a wetsuit and gloves are worn.
The really big boys can bend standard flopper shafts, but this is the most damage to equipment that you could reasonably expect.
It is alot easier (better) to use a trident... 4prong seems to be the favorite ( although spearo dave uses a matc trident), and just plant it right above the gills in the "neck" or above the eyes to attempt to stone it... although i have heard this is very hard. Then take hold of the trident immediately... but DO NOT put your fingers through the gaps of the trident to get a grip as congers frequently spin, and this can be very very painfull. And make sure you pull the conger out of his hole as quickly as possible... as if he is there for too long he will wrap around something... and they are very strong. Pull as hard as you can (tridents hold very well in a well placed shot), and then when he is in the open, cut the top of the spine with a knife, or brain it from the underneath.
If you use a standard flopper, make sure that you place the shot at a right angle to the hole, to help you guarantee that he cant hole up. Say you are using your summer gun at the time when you come across one (a 90cm with 16mm bands and a standard flopper), the chances are that you will be able to shoot it with about 15cm between the tip of the spear and the head of the conger... and it is more than likely that the spear will pass quite a way through the eel. make sure that the flopper opens, and then try to slide the eel towards the tip of the spear ( wedging it between your fist clenched around the shaft, and the flopper). Then use the same stoning method as i mentioned before.
All of this is info that i have gathered from the guys on here in preperation of spearing my first conger.So far i still ahve not seen one whils ti have been out spearing, however, i have now been told of a shallow offshore rock, where they are abundant... so next season - its on :ko :martial :crutch
Hope this has helped...
if you need more then check this thread out:
[ame="http://forums.deeperblue.net/showthread.php?t=62243"]Congers!![/ame]
Huw.