Enter criteria and click Find Words
Eighty two words start with SI, and the fourth box is an E in nearly a third of them.
L takes the third box in eleven of the eighty two, with N and R on nine each and G and T on seven. Eighteen letters appear there, so no branch is worth chasing.
SIGHT, SINCE, SILLY, SIGNS and SIXTY are the entries a puzzle is most likely to want, with SIEGE, SILKY and SIDES behind them.
E fills the fourth box in twenty five of the eighty two, thirty percent, which produces the near duplicates among SIDED, SIDER and SIDES, and again among SIRED, SIREN and SIRES.
X takes the third box in six words, giving SIXES, SIXTE, SIXTH and SIXTY. That is a real branch for a letter most players write off, and SIXTH and SIXTY are both common.
S closes twenty nine of the eighty two, thirty five percent, with R and E on nine each. Seven words repeat a letter, nine percent.
Both are common and they differ in three boxes. SIGHT tests the GH shape, which almost nothing else here uses.
It is worth remembering. Six words take X in the third box and SIXTH and SIXTY are both ordinary words.
Twenty nine, which is thirty five percent. Ruling out a plural is the biggest cut this page offers.