so i have 2020 Units in 4m and 6m...they are fine but im looking for new ones to buy
(they have just been proffesionally repaired....the 6m with a 30cm L shape tear, and the 4m with >5 tears as it got destroyed in some shore dump coming in).

So - i could simply swap them for like for like - eg new 4m and 6m (new units, new Strike + CWC, or Takoon v2)
OR given they have been repaired and i might not get much for them - i could keep them and build around it
ie buy a new 7m, and 5m.....giving me 7,6,5,4.

What dya think - replace or augment?

Having every size would mean you would wear each one out more slowly and if you shred another you can Wing on with a size up or down. You might find that you only ever use two sizes all the time which also depends on your local conditions.
I have 4, 5, and 7m Duotone Slicks as the wind here is very variable.

I say add wings. I started with a 3.5 and 5M swing. Sold those and got 2-6M BRM wings. Ended up selling the 6M. Like mentioned above, they are getting much less use individually so the quiver is lasting very well. I also can't stand being overpowered, so I really enjoy the flexibility of choosing the correct wing for the conditions.

Skymonsters in Dalkeith have the Ensis spins in which look nice. I was thinking the same thing, but my wing was in good con and got a reasonable price for it. If not worth much used then it might be worth keeping them. 2 things to ponder. Did you buy those sizes as they work best, and you will keep using those sizes and not get full benefits of new wings.
have to make a decision on which wing, when only 2 it makes it easy.
Thoughts on more wings spreads wear, yes but if buy them over a period of time likely to get better tech as new models released. nice position to be in

I would ad more.I have a 3,4,5,6 and love it.You are having lighter winds as I do so maybe ad an 5 (Magic size imo) and instead of an 7 an 8m CWC.

Fwiw, just bought a 4 and 6 m new slick, after 1 session today there is no chance i am going back to my 2020 echos, they will be on buy and sell tomorrow. i thought i might keep my 5m for an in between but nope!

can't say with your particular wings but if you buy new then going back and forth between new tech and old i reckon you'll gravitate to the newer wings and end up not really using the old ones.

Yeah but the Slick was an real upgrade over the Echo (wich was imo a pig when riding waves).
Personally I think the Unit and Slick perform overall pretty equal but do standout in different things where the echo is outright outperformed by the Slick in everything except pumping time.
I got 2 Slicks but if someone wants to trade them for units or even better Smik V2 in the same condition I dump them.

I would replace with a 4-6 then maybe add a 3 depending on the winds your going out in.
Used wings seem to sell really well here in the uk.

what is the ideal quiver - can you get away with 2 or need 3

im 80 kg in Sydney - 3 , 4.5 , 5.5/6 ?