Eu não entendi o que você quis dizer com "setando o tamanho executar o Create da classe TStringGrid". Mas, de qualquer maneira talvez o exemplo abaixo possa ajudar.
unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, Grids, StdCtrls; type TForm1 = class(TForm) Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } Grids : Array of TStringGrid; public { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} procedure TForm1.Button1Click(Sender: TObject); begin SetLength(Grids, Length(Grids) + 1); Grids[Length(Grids)-1] := TStringGrid.Create(Self); Grids[Length(Grids)-1].Parent := Self; Grids[Length(Grids)-1].Top := Length(Grids) * 50; Grids[Length(Grids)-1].Left := Length(Grids) * 50; end; end. [As partes desta mensagem que não continham texto foram removidas]