I'm sure I'm not the only one doing this but I thought I'd share my calculations on lowering my E7 head by still using the original head block & keeping the cost to a minimum.
You must at least spend $9 on the new E7SE mainshaft, that gives you 14mm right there, add to that the 8mm by using the top hole in the head block. (BTW, nothing has to be cut off the mainshaft as is necessary with the N5c, which is nice.) In addition to that I obtained another 3-4mm by drilling and additional hole in the head block perpendicular to the original holes which adds up to a total of about 25-26mm and that is one of the things I wanted to share here in particular, how I cam up with that additional amount.
Since owning an N5c and the E7 I purchased the FBL Rotors swash leveling tool which is machined to assist in the placement of the wash-out block in order to set the ideal geometry of 90+ degree angle of the wash-out arms at zero degrees blade pitch (as pointed out in the manual.) Using that tool I determined the position the head needed to be in order to maintain that same geometry since the wash-out arms were now going to be attached to the base of the head instead of the wash-out block and of course the block was going to be removed altogether.
For those who don't have FBL's tool the distance from the top of the original mainshaft to the bottom of the wash-out block is 55mm, which leaves 162mm to the bottom and that is the measurement used on the SE mainshaft. This determined the location of the new hole to be drilled in the head block and where I used my calibrated (or not so much these days) eyeball for measuring as well as drilling, hence the margin of error in my earlier comments.
It seemed that holding my head block in the drill press with my hand created a slight variation and the 3mm hole ended up about .5mm above the targeted spot, no matter, at least it was perfectly centered and my bolt went through it and the mainshaft with little effort but it did make me pay closer attention to the geometry of the wash-out arms and upon assembly my swash seemed a little high. That prompted me to investigate the recommended lengths of the swash-to-servo arms for the SE and sure enough they are about 3mm shorter, 21.25mm for the E7 vs. 18.20mm for the SE, which handled the swash position perfectly. BTW, that required about 6-7 complete turns of the each link rod.
Another part necessary is a pair of Thunder Tiger Raptor beveled washers, used for motor mounting screws, part number PV0210 and two 3X25mm cap head bolts which are used to secure the wash-out arms to the head block. The washers are positioned so the larger side is against the head block and the tapered smaller diameter side then settles w/o interference against the inner bearing race of the wash-out arm, none of the washers are needed here although I did still use one on the outside. One additional note here, if your 3X25mm bolts are shouldered, meaning threads aren't cut to the head, watch for clearance issues between the shoulder and the inner bearing race of the outer bearing, I had to file & sand that radius away and that's another reason I used one washer there.
After doing this the correct pitch link rods had to be determined, I came up with 60mm. I did purchase two necessary tools for this job that I ordered from Granger and those were a 3mm drill bit and a 2.5X0.45 thread dye of which the dye I used to turn a pair of 65mm rods available from Synergy (part number 107-065) into the 60s I needed.
So its rainy & windy out today, hence this post instead of charging batteries & packing the car so my flight results will have to be posted later.
