By going to a longer boom, & a bigger main, you're moving the CE aft. So you may get more weather helm
, & have a bit more trouble tacking, depending on your boat's underwater profile, & where the CLR is.
On the up side, on a lot of points of sail, you'll be faster. And if you go with a full battened main with a lot of roach, you may notice an increase in power without adding any weather helm
, or other negative traits.
The plans should tell you where both (the CE & CLR) are, & how she's supposed to be rigged when she's only got one mast
. Although, even then, a lot of folks have experimented with bigger, large roached mains, with positive results.
It's a guess, but if you don't have any significant weather helm now, then adding to the boom length, & main size is probably okay. Just make sure that there's sufficient supporting structure, in the area where you relocate the traveler to.