You have the correct tire size of 195/55-R16 on your Alpine. The tire is a good choice and highly recommended by GL1800 Riders.

Have to laugh at your comment regarding the 90 Degree Stem and cheap plastic support I doubt Mother Honda would install any inferior OEM parts on the F6B, Maybe not liking to some, you can be assured that both the stem/plastic support were thoroughly tested prior to going into production.

Made a suggestion to some F6B Riders about applying a dab of Permatex Gasket Maker to the wheel tit and then installing the plastic support. Those who tried it claim it works great.

Currently have just shy of 20K miles on a General G-Max and the OEM stem/support are securely in place. Same goes for the front wheel where I recently installed a Bridgestone Battlax BT45.

I do all my own "static balancing" and never encountered any issues with "tire thumping". With short bursts of speeds of 100 mph and highway cruising at 75/80 the ride is as smooth as silk

Best of luck with your Alpine. Keep us posted as to its performance

Safe Riding