problem having an inset for a stack plot

Hi,
I would like to make an inset using TPad for my plot which is made by using THStack.

  TH1D *sumtl208inset=(TH1D *)sumtl208->Clone("sumtl208inset");   sumtl208inset->GetXaxis()->SetRangeUser(1.5,3.0);

  TH1D *datainset= (TH1D*) datah->Clone("datainset");   TH1D *sumextinset=(TH1D*) sumext->Clone("sumextinset");   datainset->GetXaxis()->SetRangeUser(1.5,3.0);   sumextinset->GetXaxis()->SetRangeUser(1.5,3.0);   TH1D *sumrninset=(TH1D *)sumrn->Clone("sumrninset");   sumrninset->GetXaxis()->SetRangeUser(1.5,3.0);

  TH1D *sumintinset=(TH1D *)sumint->Clone("sumintinset");   sumintinset->GetXaxis()->SetRangeUser(1.5,3.0);

TH1D *sumeu154inset=(TH1D *)sumeu154->Clone("sumeu154inset");   sumeu154inset->GetXaxis()->SetRangeUser(1.5,3.0);

  TH1D *sumeu152inset=(TH1D *)sumeu152->Clone("sumtl208inset");   sumtl208inset->GetXaxis()->SetRangeUser(1.5,3.0);

  TH1D *sumbi207inset=(TH1D *)sumbi207->Clone("sumtl208inset");   sumbi207inset->GetXaxis()->SetRangeUser(1.5,3.0);   THStack *si=new THStack ("hsi","");

  si->Add(sumextinset);
  si->Add(sumrninset);
  si->Add(sumintinset);
  si->Add(sumtl208inset);
  si->Add(sumeu154inset);
  si->Add(sumeu152inset);
  si->Add(sumbi207inset);

    TPad *npad=new TPad("npad","", 0.405172,0.123512,0.806892,0.553572);     npad->SetFillStyle(0);
    npad->Draw();
     npad->cd();
    si->Draw("Hist");
    datainset->Draw("ep same");
     npad->Draw();

As you see in the attached plot. Instead of starting the pad from 1.5 it starts it from 0. Where ass my plan is to zoom from 1.5 to 3.0. Is that anyway to fix this problem?
Many thanks,
Nasim