Here is a diff to enable the uTP support with Transmission. It looks like the unaligned accesses issues were fixed a tad under 2 years ago.
Any Transmission users able to test especially on say sparc64? Index: Makefile =================================================================== RCS file: /home/cvs/ports/net/transmission/Makefile,v retrieving revision 1.95 diff -u -p -u -p -r1.95 Makefile --- Makefile 21 Jul 2014 14:59:17 -0000 1.95 +++ Makefile 30 Jul 2014 00:25:46 -0000 @@ -9,6 +9,7 @@ DISTNAME= transmission-${VER} PKGNAME-main= transmission-${VER} PKGNAME-gtk= transmission-gtk-${VER} PKGNAME-qt= transmission-qt-${VER} +REVISION= 0 CATEGORIES= net HOMEPAGE= http://www.transmissionbt.com/ @@ -72,8 +73,6 @@ USE_GMAKE= Yes CONFIGURE_STYLE=gnu CONFIGURE_ARGS= --disable-shared \ --enable-external-natpmp -# unaligned accesses throughout -CONFIGURE_ARGS+=--disable-utp # -I$(top_builddir)/third-party is required, but configure fails to # set it if we use external miniupnp libs. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.