There was a Stephen BENALLACK buried in Ladock 25 Apr 1716. Too late to be the one from the Wills reference.
There was a John BENALLACK buried in Ladock 22 Mar 1704
a John BENALLACK buried in Ladock 3 Jan 1729
Besides these looking at some other burials pre 1720 which may prove interesting I see....possible baptsims to explain some but no guarantees as ages are not listed.
a Mary BENALLACK in Ladock 11 Jan 1698 (dau of Stephen and Elizabeth was bap 15 Mar 1797)
a Nicholas BENALLACK buried in Ladock 18 Dec 1702 (son of John and Margery was bap 3 Dec 1702)
a Mathew BENALLACK buried in Ladock 20 Sep 1707
a Richard BENALLACK buried in Ladock 10 Jun 1714 (son of John and Margery was bap 24 Jan 1704)
a Jacob BENALLACK buried in Ladock 17 Jan 1720
a Mary BENALLACK buried in Ladock 6 Feb 1720
I am sorry I see no connection to St Just looking at early Benallack entries. Ladock, seems quite active and a few other parishes have early entries St Agnes certainly also a but of activity. Mid 1600's William was having children in Mevagissey. St Just is a far way away from these parishes.
There was baptised to Stephen and Elizabeth in Ladock (Sorry I cannot find that marriage)
Alice 8 Dec 1691
Catherine 30 Dec 1694
Mary 15 Mar 1697
Alice 26 Nov 1699
There was baptised to John and Margery in Ladock
Dorcas 16 Mar 1688 (Only lists father but seems like the first one)
Henry 6 Nov 1690
Stephen 1 Aug 1692
John 10 Jul 1694
Katherine 23 Mar 1698
Peter 3 May 1700
Nicholas 3 Dec 1702
Richard 24 Jan 1704
Cheers Kris