My Corbin is lower but wider so makes it more difficult. Maybe the Touratech low seat would work. I'm 5'11" but a long back means a 31" inseam. Anticipation and control is everything. Ride it, don't 'paddle' it. I only have to careful on cambers and ridges in the road. The 800GS has a relatively high centre of gravity so you do need to be assertive but you should be able to manage it.
You can also lower the suspension.
Ridden; GBR CYM DEU FRA ESP AND MCO ITA BEL SCT LUX CHE SMR LIE AUT NLD POL LTU LVA EST SWE FIN NOR DNK CZE SVK HUN ROU BGR GRC MKD SRB ALB MNE BIH HRV SVN MYS IRL BRA MAR PRT ARE USA ISL JPN MLT Planning; AUS TUR MDA UKR MEX BLR MNG RUS KAZ TJK KGZ SEN ZAF ZMB MWI NZL IND CPN