These are the requirements:

For fishing in France only, once a year.
Four reels.
Generally not cast.
All baits boated out, up to 200+ yards.
Very little weed.
Water crystal clear.
Fish in the lake up to 70lb +.

Thanks in advance

In reply to Post #1
How about as a leader to mono or braid?

Fox 19lb illusion in brown, proper tough stuff for the strain or Seaguar in 25lb have done me proud, in the UK as FISHING leaders

As a mainline ditched it a while ago due to its behaviours, sinks like a brick and is great for close range, long distance forget it casting, it has less stretch than mono and fished at the ranges you mention by boat you will be pulling it up from the deck all the way out I would guess but it will be interesting to see what others have to say because I have not fished it at those ranges?

In reply to Post #2
No leaders allowed mate

In reply to Post #3
OK pal, closes that option out

In reply to Post #1
All baits boated out, up to 200+ yards
I would just use braid if allowed if not I used Tiger line for years in france its never ever let me down but bloody expensive now but it does last for years

In reply to Post #5
Braid banned Gerry. Yeah, i have used Tigerline in the past and it was good. But the cost of filling 4 spools to the brim is prob going to be too costly for a once-a-year trip.

In reply to Post #6
X line probably best cost effective option

Ive been using the Ridge Monkey fluro coated mono for the last season and really like it.

In reply to Post #1
I guess bite indication might be a little slow with 200yds fluorocarbon stuck to the bottom?
Wouldn't a copolymer be more suitable?

In reply to Post #9
Tigerline 16lb

Hands down the best fluro ive used

I wouldn't use flouro at 200 yards to be honest, unless I knew the bottom was like a swimming pool. If you let it sink it could be laying on any old snag. Even the tough flouros like tiger or ace hard can succumb to a branch or weed with mussels. If you go up to the yank flouros above .40 they are probably tough but they will be hell off an open spool reel.

If you keep it tight then flouro seems to attract algae, even in crystal water it can end up looking like rope after 12 hours.

Braid is the obvious and seems daft that they don't allow it as it's the safest option.

My choice in this situation would be 20lb Korda Touchdown in brown (only as I've never used the green). It's 0.43 and tough as boots but behaves well for rope, takes on water and sinks well. Also not as bad as most mono for stretch.

In reply to Post #6
Are you after the stretch, sinking, or invisible factor?

In reply to Post #12
Can't fault x line for performance and is a lot cheaper than others. Plus you can buy a 600m spool, so enough to fill your 3 spools

In reply to Post #11
Exactly what he said

if you decide that the cost of Fluorocarbon line is to expensive and go for a quality mono I would go ESP Syncro XT 18lb thats a line that wont let you down great abrasion resistance not to stretchy and strong as hell I have had carp to high fifty's and cats to 60+with no worries fishing at range