you could try a light lead, 1oz 1 1/2 oz with a long hooklength 18inches or so, this could depend on the length of the weed, then use pva foam on the hook to slow the decent of the hook bait so it rests ontop ot the weed and does not catch up in it, also critically balanced hookbaits/pop ups may help in this situation?
you could try the pva bag aproach as this will flatten/sit ontop of the weed?
if there are alot of silver fish, smaller fish in the lake you could prebait with particals, hemp/pellets/corm etc and let the fish clear you a spot over time?
or even try casting your rigs out when the sun has gone down as this is when the weed will be at its lowest (stooped), as during the daylight weed will tend to "reach" towards the sun.
just a few ideas you could try, im not the best at fishing in and amongst weed so maybe others could give you better ideas/advise????