As a suggestion, when landing single engine you could simply have a look at the performance tables for the airfield you're landing at (assuming you have them and not diverting into a completely unknown field).
If your weight is approaching the WAT limit (sometimes called climb limit) for the temperature at the field then consider a bleeds off landing. (You might also want to look at the figures from the "packs off" tables as well. If by any chance your weight is above that then bear in mind at that field, even bleeds off, in the event of a go-around your climb performance won't be what you expect!!
Hope that helps.