Of course we all know from the recent thread that an engine fund forms no part of the value of a share.
So you should have nothing to worry about
As your case demonstrates, a share with an engine fund certainly does have a higher value than one with the same aircraft without an engine fund.
Seriously though, what would happen when the engine was due to be replaced? I presume the cost of the new engine would have been split 10 ways? Or did your agreement with the flying club extend to them replacing the engine, as well as doing the maintenance? If the later, was there a written agreement specifying this?
In the more likely case that each member must pay for 1/10 of the engine replacement cost, then nothing has changed. Whoever holds the six shares, currently owned by the flying club, will have to pay 6/10 of the cost of the new engine (plus 1/10 if they already own another share).
Obviously your ongoing costs will have to be looked at if you now have to start paying for maintenance, parking, landing etc, and when reviewing them you would be wise to include an amount to start building up an engine fund as you go along.
dp