17LT, I should have mentioned.

Having recently completed my Ches 17LT I feel qualified to answer this one!   The position of the forward beam is - within sensible limits - quite flexible, so removing it to plane, then relocating it within a few inches of its original postion will be of no consequence.   Just trim an equal amount off both ends so it retains its symmetric acros-the-deck curvature.   And just FYI, because the aft deck is pretty flat too, I installed a couple of extra 'beamlets' to give the deck there a bit of additional support, in case I or anybody else has to clamber onto the deck in recovery mode (!).   My deck is 3mm thick, by the way.

The 'beamlets' were cut from 4mm ply, about 1" deep, epoxied for stiffness, then just dropped-in and filleted on edge at what looked about the right spot.   The first is 3790mm from the bow, the second 4468mm from the bow.   Again, not at all critical, just wherever looked about right.   (I recorded these inside hull measurements before the deck went on, in case I ever need to know where - f'rinstance - to drill for a fitting, or whatever.   Saves guessing what's beneath).

Enjoy the rest of the build.

Wordsmith