I think medium well is a little too done for an eye round. Your going to be close to shoe leather territory. Eye round is pretty much fat free and at medium well there won't be enough moisture left to keep things lubricated. I base this on the personal experience of eating many of my mothers overdone eye rounds on Sunday dinners.
Make sure to have plenty of gravy available.

Roast at 350 degrees F for 30 to 45 minutes. Check the internal temp. You're looking for 150 degrees F for med well.

Here's are the USDA guidelines for internal temperature: http://www.fsis.usda.gov/Is_It_Done_Yet/Brochure_Text/index.asp

Here's a temp chart: http://whatscookingamerica.net/Information/MeatTemperatureChart.htm

And here's a nice sounding recipe too! http://www.epicurious.com/recipes/food/views/Roast-Beef-for-Beef-on-Weck-102025