Drawing 27 and 27A
It is drawing 27 and 27A in my set of drawings, but they are for the older (not match-drilled) fuselage, so the numbering may have changed.
In any case, the rear spar of the horizontal stabilizer is supposed to go behind the vertical bars, but clamp right to them. It appears your previous builder for some reason set up the stabilizer too far far aft.
Have the holes been drilled through the rear spar and vertical bars yet?
-If yes, then it appears the previous builder for some reason decided to shift the stabilizer aft. Strange. Is the incidence angle correct? There are some spacers that need to be inserted temporarily to hold the stabilizer at the right incidence angle while drilling.
-If no, then I wonder why the previous builder drilled the forward holes at this stage.
Lets see if we can brain-storm some fixes for you.
One option for you would be to make a set of shim plates to fit between the vertical bars and the rear spar. This, plus using appropriate length bolts, should be fine. But a few other issues are going to appear down the road because of this. One is the possibility that the elevator horn will interfere with something that limits the 'up' elevator travel. Note that the angle F-812B is made to provide the up elevator stop, and you notch it as needed so that the elevator horn hits it at the correct elevator angle. Shifting the stabilizer aft is going to require a deeper notch into the F-812B. Hopefully the elevator horn won't hit anything else. The next issue is that the joint of the forward fin spar to the forward stabilizer spar is going to be different. The F-681 joiner is going to be shifted aft too, so that it will want to mount to the aft face of the forward fin spar, rather than the forward face as shown on the plans. You will also need to make a different spacer like F-885 to fill any gap, but it is hard to predict where that is all going to fit until you mount the stabilizer and the rear fin spar. The last issue, a minor one, will be that the fiberglass empennage fairing is not going to fit very well. That's OK, they usually do not fit great anyway -- I did some custom fiberglass work to make my fairing fit around and under the stabilizer leading edge, and this fit issue would be resolved then.
Another option might be to replace the components in the fuselage that have been drilled, so that the stabilizer could be mounted in its proper location, shifted 3/16" forward from where it is now. The F-810C angle would not be too difficult to replace. Unfortunately, the outboard holes also go through the upper longeron, F-887. This is a problem. You don't really want to splice a new piece of longeron in place of the old, although that could be done. With a new F-810C angle providing good bolt bearing area, it might be OK to just make a second hole in the longeron. Not generally accepted practice, for sure, and definitely would want to get buy-in from Vans. You would have to be very careful drilling the new hole, because if the drill gets into the old hole at all, it is going to steer the drill wrong. Could put an aluminum plug in the old hole first, that would help. You would end up with two holes through the longeron that are right next to each other, like a figure-8. Again, this is not generally allowed so you would want to discuss it with Vans. The saving detail here is that the hole would go through a new F-810C angle in the proper place and that would hold everything together.