Padraig Harrington believes Port Royal’s signature 16th hole is quite possibly the toughest par-three in all of golf.There are several par threes that strike fear into Harrington’s heart, like the 17th holes at Sawgrass and Wachovia, but none more so than Port Royal’s breathtaking 16th.It was the only hole where the affable Irishman dropped a shot during yesterday’s opening round of the PGA Grand Slam.“There are plenty of par threes that strike fear in me. I could give you a long list,” said Harrington, who shot a sparkling five-under-par 66.“In terms of a raw hole, the 16th hole here is as tough a golf hole as you could ever see. You put the whole combination together, it’s as good a golf hole as you could ever see, hopefully I’ll get through it tomorrow in stroke play.“I did a show for the Golf Channel yesterday hitting wedges in there and I thought it was a tight hotel hit from 107 yards.“It’s not great when you’re walking up a par three to see the drop zone.”Harrington admitted there’s an element of the exhibition about the Grand Slam the PGA Tour’s annual curtain call with all four players enjoying the relaxed and chatty mood at Port Royal yesterday.It’s an environment that seems to suit Harrington, who joked that the best chance his playing partners had of cutting into his two-shot lead would be to stop talking to him.“You know what, every day I play, I always try to make an effort to enjoy the day, talk to my playing partners,” said the 41-year-old, who was picked as an alternate three days ago for British Open champion Ernie Els.“Today it was better than ever. We were all very relaxed out there. Everybody was up for a chat. Some days you can play with a guy who maybe doesn’t want to talk back, so you can keep talking.“Today everybody was enjoying it, and you know, selfishly, I play better when the whole group enjoys it. If the guys have any sense, they shouldn’t talk to me tomorrow.”Harrington believes his biggest threat to the pink jacket could be the big-hitting Bubba Watson, whose accuracy with the driver never ceases to amaze the Irishman.“(Watson) hits it so straight. It’s unbelievable how straight he hits the ball,” said Harrington, a play-off loser the two times he qualified for the Grand Slam.“It is incredible, guys can hit it a long way, and Bubba is long, there’s no doubt about it, but he’s incredibly straight.“The couple of lines he took out there, he just never looks like he’s going to miss it and hit it off-line, which is quite unique to be able to hit it that far and so straight.“It’s unusual to see the long hitter always reaching for the driver, and it’s obviously the best club in his bag and certainly it’s incredible how straight he hits it.”