Fitting Cylinder to Boiler

Today i fitted the cylinder to the boiler came across a problem when fitting the studs under the cylinder drain. I shortened these by about 2mm inserted from the under side and locked 2 nuts on and put the cylinder on then screwed the studs in. may be these studs should be fitted first rather than the top studs in the instructions? Also the blast pipe hole is only about 6mm it seems a lot small than in the picture is this correct.

Keith