The May field in Offshore Mexico is difficult to drill due to the presence of boulders and conglomerates within the top hole section. The interval is traditionally drilled with a conventional 18 1/2" bit and BHA. However, an enlarged hole is planned as contingency to provide an improved cement bond with the casing utilized. Due to casing drift, this requires the use of hole opening string tools to provide a final hole diameter of 21".Prior hole opening runs have endured significant vibration and resultant mechanical damage to the tools and pilot bits. An offset well utilized commercial concentric hole opening tools that have cutter blocks that can be activated and retracted so that it can be pulled back through the casing. The hole opening section required a total of eight string reamer tools and three 18 1/2" pilot bits to reach TD.A unique eccentric string reamer tool was selected that utilizes a mid-reamer section for improved string stabilization and hole enlargement. This was coupled with an eccentric vibration dampening tool, specifically positioned in the string to disturb damaging vibration harmonics. In order to refine parameter recommendations, Finite Element Analysis Software was utilized to model the harmonic behavior of the drill string. This assembly, combined with a point-the-bit rotary steerable tool drilled this challenging hole section in 9 days, delivering low vibrations and gauge hole. An estimated $4.4 M was saved compared to the original well plan and $11.5 million compared to the direct offset well for this interval.