As Xausa has pointed out quite correctly, cast and drop have the realy critical impact on the handeling of a DR or shotgun. LOP is important but can easily be adjusted within realistic paramiters.
Everbody shoots an instintive weapon, either a SG or DR better if it is fitted for them. Alas too few of us do this adapting to off the shelf guns or old DR's built for monsters or dwarfs.
Cast and drop is what brings the sighting plane into our instintive vision. LOP is influenced all the time by what we are wearing anyway (again within realistic parmiters)

If the DR maker is not offering fitting (what is your budget ?) then it would be wise to visit a good shooting school with an adjustable try gun and shoot a few round of sporting, tinkering with the fit until you have it right. It would be best of course if there is an experienced fitter there wih you. It is money well spent.

Regards